gh-136421: Fix crash when _datetime is been initialized in multiple sub-interpreters

[aisk]

• Issue: Import _datetime in sub-interpreters in the same time may crash the process #136421

[ZeroIntensity]

I think we need a more fundamental fix that prevents static types from being initialized concurrently. This is sort of a known issue, see #129817.

[bedevere-app]

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[ZeroIntensity]

Please add a test. I'm still not fully convinced that this is the right approach; _PyStaticType_InitForExtension should be thread-safe on its own, or at least in the places where it's used.

I think the problem is that _datetime is special and has static types (because they need to be exposed via the capsule). Instead of initializing them in the module's execution function, let's do it during interpreter initialization in pycore_interp_init.

[neonene]

An alternative would be to make _interpreters module import _datetime when running the main interpreter.

[aisk]

Due to issue #136423, importing _datetime into a sub-interpreter concurrently still results in a crash, even after this change, so it's hard to write a test. I also feel that this is not the correct way to fix the root cause, and this PR is more like a workaround.

I'll continue to investigate #136423, as they appear to have the same root cause. Maybe we can find a better way to address them. So maybe we can wait sometime before continue this PR?

[ZeroIntensity]

I've put up #136583 as an alternative that avoids locking, at the cost of moving _datetime to a static library.