Report incompatible ast-serialize versions clearly

[sjh9714]

Fixes #21412.

This checks the installed ast-serialize distribution version before the native parser serializes AST data. Incompatible versions now produce a clear mypy error instead of letting parallel checking deserialize incompatible data and report an internal error.

The check is cached after a successful validation, and missing distribution metadata keeps the existing manual/native-parser behavior unchanged.

Testing:

• .venv/bin/python -m pytest -n0 mypy/test/test_nativeparse.py -k ast_serialize_version -q
• .venv/bin/python -m pytest -n0 mypy/test/test_nativeparse.py -q
• .venv/bin/python runtests.py self
• PATH="$PWD/.venv/bin:$PATH" .venv/bin/python runtests.py lint
• git diff --check
• Verified a temporary venv with ast-serialize==0.2.3 reports mypy: error: ast-serialize 0.2.3 is too old; mypy requires ast-serialize>=0.5.0,<1.0.0 for mypy --num-workers=2.

Note: I used Codex while preparing this change, and reviewed the final diff and ran the listed checks locally.

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅