Nightly Clippy doesn't like having lints and groups at the same priority.
I'm not sure if this is a false positive or not (see
<rust-lang/rust-clippy#12270> for a related
discussion) but it seems reasonable to make the change regardless.

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
    --> Cargo.toml:35:1
     |
  35 | rust_2018_idioms = "warn"
     | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
  36 | single_use_lifetimes = "warn"
     | -------------------- has the same priority as this lint
     |
     = note: the order of the lints in the table is ignored by Cargo
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
     = note: `#[deny(clippy::lint_groups_priority)]` on by default
  help: to have lints override the group set `rust_2018_idioms` to a lower priority
     |
  35 | rust_2018_idioms = { level = "warn", priority = -1 }
     |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
    --> Cargo.toml:35:1
     |
  35 | rust_2018_idioms = "warn"
     | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
  36 | single_use_lifetimes = "warn"
     | -------------------- has the same priority as this lint
     |
     = note: the order of the lints in the table is ignored by Cargo
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
     = note: `#[deny(clippy::lint_groups_priority)]` on by default
  help: to have lints override the group set `rust_2018_idioms` to a lower priority
     |
  35 | rust_2018_idioms = { level = "warn", priority = -1 }
     |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
  --> Cargo.toml:11:1
   |
11 | rust_2018_idioms = "warn"
   | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
12 | single_use_lifetimes = "warn"
   | -------------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
   = note: `-D clippy::lint-groups-priority` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::lint_groups_priority)]`
help: to have lints override the group set `rust_2018_idioms` to a lower priority
   |
11 | rust_2018_idioms = { level = "warn", priority = -1 }
   |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `all` has the same priority (0) as a lint
  --> Cargo.toml:16:1
   |
16 | all = "warn" # Downgrade deny-by-default lints
   | ^^^   ------ has an implicit priority of 0
17 | pedantic = "warn"
18 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `all` to a lower priority
   |
16 | all = { level = "warn", priority = -1 } # Downgrade deny-by-default lints
   |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `pedantic` has the same priority (0) as a lint
  --> Cargo.toml:17:1
   |
17 | pedantic = "warn"
   | ^^^^^^^^   ------ has an implicit priority of 0
18 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `pedantic` to a lower priority
   |
17 | pedantic = { level = "warn", priority = -1 }
   |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
  --> Cargo.toml:70:1
   |
70 | rust_2018_idioms = "warn"
   | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
71 | single_use_lifetimes = "warn"
   | -------------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
   = note: `-D clippy::lint-groups-priority` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::lint_groups_priority)]`
help: to have lints override the group set `rust_2018_idioms` to a lower priority
   |
70 | rust_2018_idioms = { level = "warn", priority = -1 }
   |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `all` has the same priority (0) as a lint
  --> Cargo.toml:75:1
   |
75 | all = "warn" # Downgrade deny-by-default lints
   | ^^^   ------ has an implicit priority of 0
76 | pedantic = "warn"
77 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `all` to a lower priority
   |
75 | all = { level = "warn", priority = -1 } # Downgrade deny-by-default lints
   |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `pedantic` has the same priority (0) as a lint
  --> Cargo.toml:76:1
   |
76 | pedantic = "warn"
   | ^^^^^^^^   ------ has an implicit priority of 0
77 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `pedantic` to a lower priority
   |
76 | pedantic = { level = "warn", priority = -1 }
   |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
  --> Cargo.toml:54:1
   |
54 | rust_2018_idioms = "warn"
   | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
55 | single_use_lifetimes = "warn"
   | -------------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
   = note: `-D clippy::lint-groups-priority` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::lint_groups_priority)]`
help: to have lints override the group set `rust_2018_idioms` to a lower priority
   |
54 | rust_2018_idioms = { level = "warn", priority = -1 }
   |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `all` has the same priority (0) as a lint
  --> Cargo.toml:59:1
   |
59 | all = "warn" # Downgrade deny-by-default lints
   | ^^^   ------ has an implicit priority of 0
60 | pedantic = "warn"
61 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `all` to a lower priority
   |
59 | all = { level = "warn", priority = -1 } # Downgrade deny-by-default lints
   |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `pedantic` has the same priority (0) as a lint
  --> Cargo.toml:60:1
   |
60 | pedantic = "warn"
   | ^^^^^^^^   ------ has an implicit priority of 0
61 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `pedantic` to a lower priority
   |
60 | pedantic = { level = "warn", priority = -1 }
   |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
  --> Cargo.toml:38:1
   |
38 | rust_2018_idioms = "warn"
   | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
39 | single_use_lifetimes = "warn"
   | -------------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
   = note: `-D clippy::lint-groups-priority` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::lint_groups_priority)]`
help: to have lints override the group set `rust_2018_idioms` to a lower priority
   |
38 | rust_2018_idioms = { level = "warn", priority = -1 }
   |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `all` has the same priority (0) as a lint
  --> Cargo.toml:43:1
   |
43 | all = "warn" # Downgrade deny-by-default lints
   | ^^^   ------ has an implicit priority of 0
44 | pedantic = "warn"
45 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `all` to a lower priority
   |
43 | all = { level = "warn", priority = -1 } # Downgrade deny-by-default lints
   |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `pedantic` has the same priority (0) as a lint
  --> Cargo.toml:44:1
   |
44 | pedantic = "warn"
   | ^^^^^^^^   ------ has an implicit priority of 0
45 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `pedantic` to a lower priority
   |
44 | pedantic = { level = "warn", priority = -1 }
   |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
  --> Cargo.toml:70:1
   |
70 | rust_2018_idioms = "warn"
   | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
71 | single_use_lifetimes = "warn"
   | -------------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
   = note: `-D clippy::lint-groups-priority` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::lint_groups_priority)]`
help: to have lints override the group set `rust_2018_idioms` to a lower priority
   |
70 | rust_2018_idioms = { level = "warn", priority = -1 }
   |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `all` has the same priority (0) as a lint
  --> Cargo.toml:75:1
   |
75 | all = "warn" # Downgrade deny-by-default lints
   | ^^^   ------ has an implicit priority of 0
76 | pedantic = "warn"
77 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `all` to a lower priority
   |
75 | all = { level = "warn", priority = -1 } # Downgrade deny-by-default lints
   |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `pedantic` has the same priority (0) as a lint
  --> Cargo.toml:76:1
   |
76 | pedantic = "warn"
   | ^^^^^^^^   ------ has an implicit priority of 0
77 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `pedantic` to a lower priority
   |
76 | pedantic = { level = "warn", priority = -1 }
   |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
   --> Cargo.toml:118:1
    |
118 | rust_2018_idioms = "warn"
    | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
119 | single_use_lifetimes = "warn"
    | -------------------- has the same priority as this lint
    |
    = note: the order of the lints in the table is ignored by Cargo
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
    = note: `-D clippy::lint-groups-priority` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::lint_groups_priority)]`
help: to have lints override the group set `rust_2018_idioms` to a lower priority
    |
118 | rust_2018_idioms = { level = "warn", priority = -1 }
    |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `all` has the same priority (0) as a lint
   --> Cargo.toml:123:1
    |
123 | all = "warn" # Downgrade deny-by-default lints
    | ^^^   ------ has an implicit priority of 0
124 | pedantic = "warn"
125 | as_ptr_cast_mut = "warn"
    | --------------- has the same priority as this lint
    |
    = note: the order of the lints in the table is ignored by Cargo
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `all` to a lower priority
    |
123 | all = { level = "warn", priority = -1 } # Downgrade deny-by-default lints
    |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `pedantic` has the same priority (0) as a lint
   --> Cargo.toml:124:1
    |
124 | pedantic = "warn"
    | ^^^^^^^^   ------ has an implicit priority of 0
125 | as_ptr_cast_mut = "warn"
    | --------------- has the same priority as this lint
    |
    = note: the order of the lints in the table is ignored by Cargo
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `pedantic` to a lower priority
    |
124 | pedantic = { level = "warn", priority = -1 }
    |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270

```
error: lint group `rust_2018_idioms` has the same priority (0) as a lint
  --> Cargo.toml:50:1
   |
50 | rust_2018_idioms = "warn"
   | ^^^^^^^^^^^^^^^^   ------ has an implicit priority of 0
51 | single_use_lifetimes = "warn"
   | -------------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
   = note: `-D clippy::lint-groups-priority` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::lint_groups_priority)]`
help: to have lints override the group set `rust_2018_idioms` to a lower priority
   |
50 | rust_2018_idioms = { level = "warn", priority = -1 }
   |                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `all` has the same priority (0) as a lint
  --> Cargo.toml:55:1
   |
55 | all = "warn" # Downgrade deny-by-default lints
   | ^^^   ------ has an implicit priority of 0
56 | pedantic = "warn"
57 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `all` to a lower priority
   |
55 | all = { level = "warn", priority = -1 } # Downgrade deny-by-default lints
   |       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

error: lint group `pedantic` has the same priority (0) as a lint
  --> Cargo.toml:56:1
   |
56 | pedantic = "warn"
   | ^^^^^^^^   ------ has an implicit priority of 0
57 | as_ptr_cast_mut = "warn"
   | --------------- has the same priority as this lint
   |
   = note: the order of the lints in the table is ignored by Cargo
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lint_groups_priority
help: to have lints override the group set `pedantic` to a lower priority
   |
56 | pedantic = { level = "warn", priority = -1 }
   |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

Cargo.lock was updated to version 4 manually.
All Git refs in our Cargo.lock appear to be encoded correctly.
See:
- rust-lang/cargo#12280
- rust-lang/cargo#12852

The clippy::incompatible_msrv lint may be useful in the future.
We currently do not specify rust-version in Cargo.toml.
Our libraries are not designed to be used outside Grandine.
rust-toolchain.toml makes rust-version redundant for builds inside this repository.
See:
- https://doc.rust-lang.org/1.78.0/cargo/reference/manifest.html#the-rust-version-field
- https://rust-lang.github.io/rust-clippy/rust-1.78.0/#/incompatible_msrv

The clippy::lint_groups_priority lint produces false positives:
- rust-lang/cargo#12918 (comment)
- rust-lang/rust-clippy#12270
Luckily, lints inherited from a workspace do not trigger it.
The issue appears to be fixed in rust-lang/rust-clippy#12827.

The reason public functions trigger clippy::single_call_fn is actually our setting of avoid-breaking-exported-api.
We assumed it was a bug.

rust-lang/rust-clippy#12270

rust-lang/rust-clippy#12270