Feature or enhancement

Now that we havemypy infrastructure readyhttps://github.com/python/cpython/blob/main/.github/workflows/mypy.yml we can add more things to the test.

https://github.com/python/cpython/tree/main/Tools/peg_generator hasmypy.ini and annotations. So, let's check it as well.

How I plan to do it (separate PRs):

1. Start small with the CI job itself and initial fixes
2. Addtypes-setuptools dependency and fix more problems
3. Update config to be stricter and refactor

Linked PRs

• gh-108455: Runmypy onTools/peg_generator #108456
• gh-108455: Simplify the peg_generator mypy config #108620
• gh-108455: peg_generator: make the mypy config slightly stricter #108627
• gh-108455: Usestrict_optional=True forgrammar_parser #108629
• gh-108455: peg_generator: install two stubs packages before running mypy #108637
• gh-108455: peg_generator: usetypes-setuptools==68.1.0.1 in CI #108697
• gh-108455: peg_generator: enable mypy's--warn-unreachable setting andredundant-expr error code #109160