[TRI-2208] Bulk import environment variables (v3)

[matt-aitken]

The ability to copy+paste a load of environment variables at once.

Important considerations

• We have multiple environments, so you'll want to select an environment (or possibly multiple? Possibly a bit weird given they're normally different across environments).
• What should we do if there's an existing env var in that environment with the same key? Just override? Or possibly it should have a red warning next to it so you can choose to remove it before you confirm?

_TRI-2208

[pkpio]

I think vercel's approach should work well enough. Each time you are adding a variable(s), you have the choice of selecting environments to import to.

If a variable already exists in an environment, it refuses to import.

[manurana]

Maybe also a CLI util (a la SST.dev)

• import from a file (option of json/env)
• export to a file