gh-117398: Use Per-Interpreter State for the _datetime Static Types (gh-119929)

We make use of the same mechanism that we use for the static builtin types.  This required a few tweaks.

The relevant code could use some cleanup but I opted to avoid the significant churn in this change.  I'll tackle that separately.

This change is the final piece needed to make _datetime support multiple interpreters.  I've updated the module slot accordingly.

Python/crossinterp_exceptions.h

@@ -90,6 +90,6 @@ static void
 fini_exceptions(PyInterpreterState *interp)
 {
     // Likewise with _fini_not_shareable_error_type().
-    _PyStaticType_Dealloc(interp, &_PyExc_InterpreterNotFoundError);
-    _PyStaticType_Dealloc(interp, &_PyExc_InterpreterError);
+    _PyStaticType_FiniBuiltin(interp, &_PyExc_InterpreterNotFoundError);
+    _PyStaticType_FiniBuiltin(interp, &_PyExc_InterpreterError);
 }