Add conformance tests for PEP 702's @deprecated

[InSyncWithFoo]

Fixes #1821.

I'm not sure how to make Pytype run properly (#1758), probably because I'm using Rye, so I'm skipping manual tests.

[erictraut]

Thanks for doing this!

This looks pretty good, but I think the three test files should be combined into one for the reasons I mention in the comment.

You should also run the test suite and manually score the four type checkers, update the corresponding toml files, and do a final run to generate the conformance summary report.

[InSyncWithFoo]

I'm not sure why, but Pyre's results changed drastically. Are the changes supposed to be committed?

[erictraut]

I'm not sure what to do about the pyre tests. I don't think we can commit the PR as is. Options:

1. You find a way to run the pyre tests on your machine.
2. Someone else runs the tests and updates the PR on your branch before you commit it.
3. You revert all of the pyre test results, we merge your PR, and then I immediately follow it up with another PR that addresses the pyre results.

Option 1 is cleanest if you're able to do it. If that's not feasible, then option 3 might work the best.

[JelleZijlstra]

I'm running the script locally now and will update pyre.

[erictraut]

Thanks again for doing this! The latest draft looks good to me.