GH-118095: Make invalidating and clearing executors memory safe (GH-118459)

Objects/codeobject.c

@@ -1504,7 +1504,8 @@ clear_executors(PyCodeObject *co)
     assert(co->co_executors);
     for (int i = 0; i < co->co_executors->size; i++) {
         if (co->co_executors->executors[i]) {
-            _Py_ExecutorClear(co->co_executors->executors[i]);
+            _Py_ExecutorDetach(co->co_executors->executors[i]);
+            assert(co->co_executors->executors[i] == NULL);
         }
     }
     PyMem_Free(co->co_executors);