Issue #25421: __sizeof__ methods of builtin types now use dynamic basic size.

This allows sys.getsize() to work correctly with their subclasses with
__slots__ defined.

Objects/listobject.c

@@ -2324,7 +2324,7 @@ list_sizeof(PyListObject *self)
 {
     Py_ssize_t res;
 
-    res = sizeof(PyListObject) + self->allocated * sizeof(void*);
+    res = _PyObject_SIZE(Py_TYPE(self)) + self->allocated * sizeof(void*);
     return PyLong_FromSsize_t(res);
 }