Pyright CI test doesn't recognize `requires_python` in `METADATA.toml`

[Avasam]

The test pyright: Run test cases can fail for older Python versions due to using newer features. For example, in #13968 (comment) I typed a class with a dataclass decorator using kwargs added to Python 3.10. Despite setting requires_python = ">=3.10" in stubs/networkx/METADATA.toml

Example run (whilst the build logs are still available) https://github.com/python/typeshed/actions/runs/14921000784/job/41916216049?pr=13968

One possible solution with the current setup, is to collect stubs whose requires_python don't match the current Python version, and pass them to pyright's file exclusion.

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Similarly, if running tests/runtests.py on a third-party stub, requires_python should be taken into account rather than only relying on _PYTHON_VERSION.
Edit: #14051

[srittau]

This is basically a duplicate of #10722. Closing this here as there is already some discussion there.