gh-124153: Implement PyType_GetBaseByToken() and Py_tp_token slot

[neonene]

• Issue: Add PyType_GetBaseByToken function with Py_tp_token slot #124153

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📚 Documentation preview 📚: https://cpython-previews--124163.org.readthedocs.build/

[neonene]

I'll check this and PoC version again.

[encukou]

Looks great, thank you!
I have just one style suggestion. But if you'd like to keep it we can merge the PR as it is.

[neonene]

When I observed a good performance, the line had a typo (missing a NOT), though check_base_by_token() was unused during a PGO test. The telco got slower by 5-10% once I corrected, which was actually fixed by one of the following:

• Use if-else statement

• Replace _PyType_HasFeature() with the public PyType_HasFeature(), not with ineffective (type->tp_flags & Py_TPFLAGS_HEAPTYPE)

They are not used in PyType_GetBaseByToken().

[neonene]

I think I've finished. When checking a type without a result, this may be a bit slower than the draft PR, not trained well for now.