_PyStaticType_InitBuiltin should not exist.

[markshannon]

Part three in an ongoing series...

Following on from #96458 and #101603.

Static, builtin classes must be sharable across interpreters.
Therefore, they should be immortal and idempotent immutable. Ideally they should be immutable, but we can tolerate a bit of initialization as long as it is idempotent and thread-safe.
Therefore _PyStaticType_InitBuiltin should not exist.
We can also free up the _Py_TPFLAGS_STATIC_BUILTIN flag, as we are running low on flags.

AFAICT _PyStaticType_InitBuiltin sets an index for accessing the subclasses dict on the interpreter, and calls PyType_Ready. That's all.
PyType_Ready should be a no op on static builtin classes. (If it isn't, then that's another issue we need to add.)
Setting the subclass index can be done lazily, as many builtin classes are never subclassed.
There is no reason for the index to be distinct from the version tag, so we should use that, and statically initialize it for int, type, etc.

@ericsnowcurrently @kumaraditya303
Any more of these static init/dealloc functions? They should all go.

[ericsnowcurrently]

FWIW, everything you've said makes sense. 🙂