Allow ClassDB to create a Object without postinitialization for GDExtension.

core/object/object.cpp

@@ -207,10 +207,13 @@ void Object::cancel_free() {
 	_predelete_ok = false;
 }
 
-void Object::_postinitialize() {
-	_class_name_ptr = _get_class_namev(); // Set the direct pointer, which is much faster to obtain, but can only happen after postinitialize.
+void Object::_initialize() {
+	_class_name_ptr = _get_class_namev(); // Set the direct pointer, which is much faster to obtain, but can only happen after _initialize.
 	_initialize_classv();
 	_class_name_ptr = nullptr; // May have been called from a constructor.
+}
+
+void Object::_postinitialize() {
 	notification(NOTIFICATION_POSTINITIALIZE);
 }
 
@@ -2129,6 +2132,7 @@ bool predelete_handler(Object *p_object) {
 }
 
 void postinitialize_handler(Object *p_object) {
+	p_object->_initialize();
 	p_object->_postinitialize();
 }