Swift: Use entities in reorder directives

[cklin]

This PR changes reorder directives in upgrade/downgrade scripts to use proper entity type names, instead of using int as generic stand-in for entity types.

[geoffw0]

I notice that CI has run "Upgrades Checks" on this PR. I would very much like to build confidence that these scripts are behaving correctly after the changes, without having to fiddle around with them on my own machine. Two questions:

1. what do the upgrade checks actually do?
2. I don't see Swift in the list of languages being checked, what's going on there?

I'll be happy to approve this and #16418 once I have some confidence of the test coverage.

[cklin]

I notice that CI has run "Upgrades Checks" on this PR. I would very much like to build confidence that these scripts are behaving correctly after the changes, without having to fiddle around with them on my own machine. Two questions:

1. what do the upgrade checks actually do?

The "Upgrades Checks" workflow takes every upgrade (and downgrade) script for the checked languages and (a) creates an empty database then (b) applies the script to the empty database.

What is checked: that the upgrade/downgrade script compiles successfully and passes the static validation checks implemented in the CLI.

What is not checked: that upgrade/downgrade applies successfully on a non-empty database and that the before and after databases produce the same query results (for any query).

For the changes in this PR, the static checks performed by "Upgrades Checks" should be sufficient to ensure that we did not break anything, if the workflow actually covers swift.

2. I don't see Swift in the list of languages being checked, what's going on there?

I think that is most likely an unintentional omission. I will open a separate PR to address the issue.