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.

Python/pylifecycle.c

@@ -760,6 +760,11 @@ pycore_init_types(PyInterpreterState *interp)
         return status;
     }
 
+    status = _PyDateTime_InitTypes(interp);
+    if (_PyStatus_EXCEPTION(status)) {
+        return status;
+    }
+
     return _PyStatus_OK();
 }