gh-136421: Load _datetime static types during interpreter initialization (GH-136583)

`_datetime` is a special module, because it's the only non-builtin C extension that contains static types. As such, it would initialize static types in the module's execution function, which can run concurrently. Since static type initialization is not thread-safe, this caused crashes. This fixes it by moving the initialization of `_datetime`'s static types to interpreter startup (where all other static types are initialized), which is already properly protected through other locks.

Modules/Setup.bootstrap.in

@@ -12,6 +12,8 @@ posix posixmodule.c
 _signal signalmodule.c
 _tracemalloc _tracemalloc.c
 _suggestions _suggestions.c
+# needs libm and on some platforms librt
+_datetime _datetimemodule.c
 
 # modules used by importlib, deepfreeze, freeze, runpy, and sysconfig
 _codecs _codecsmodule.c