Fix generate_self_schema for Python 3.12+

[JelleZijlstra]

For reference: https://github.com/python/cpython/blob/8c96850161da23ad2b37551d2a89c7d4716fe024/Lib/typing.py#L916

Ran into this trying to install pydantic on 3.14.

Change Summary

Related issue number

Checklist

• Unit tests for the changes exist
• Documentation reflects the changes where applicable
• Pydantic tests pass with this pydantic-core (except for expected changes)
• My PR is ready to review, please add a comment including the phrase "please review" to assign reviewers

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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[codspeed-hq]

CodSpeed Performance Report

Merging #1299 will not alter performance

_{Comparing JelleZijlstra:patch-1 (e4deb7e) with main (88a8a30)}

Summary

✅ 155 untouched benchmarks

[sydney-runkle]

Great, thank you! Looks good to me!

[davidhewitt]

@JelleZijlstra it's worth noting that I have no idea what parts may be broken under 3.14 due to the PyO3 layer - we can try to add patches to PyO3 if needed but hopefully the majority works. If in doubt you might want to try this branch which at least attempts to catch up with 3.13: PyO3/pyo3#4184

[JelleZijlstra]

Thanks! Yes, when I tried locally I got an error telling me to use an env var that tries to use the stable ABI, but then I got the error that this PR fixes. I'll look into it some more later.