feat(obj_class) separate lv_obj_class_create_obj into lv_obj_class_create_obj and lv_obj_class_init_obj

It allows using the new object reference somewhere before initializing it. Usuful for the Micropython binding.

src/core/lv_obj.c

@@ -174,7 +174,10 @@ void lv_deinit(void)
 
 lv_obj_t * lv_obj_create(lv_obj_t * parent)
 {
-    return lv_obj_class_create_obj(&lv_obj_class, parent, NULL);
+    LV_LOG_INFO("begin")
+    lv_obj_t * obj = lv_obj_class_create_obj(MY_CLASS, parent);
+    lv_obj_class_init_obj(obj);
+    return obj;
 }
 
 /*=====================