refactor : operation system

Assets/YooAsset/Runtime/OperationSystem/AsyncOperationBase.cs

@@ -152,6 +152,14 @@ namespace YooAsset
             return IsDone;
         }
 
+        /// <summary>
+        /// 清空完成回调
+        /// </summary>
+        protected void ClearCompletedCallback()
+        {
+            _callback = null;
+        }
+
         /// <summary>
         /// 等待异步执行完毕
         /// </summary>

Assets/YooAsset/Runtime/OperationSystem/GameAsyncOperation.cs

@@ -15,6 +15,10 @@ namespace YooAsset
         {
             OnAbort();
         }
+        internal override void InternalWaitForAsyncComplete()
+        {
+            OnWaitForAsyncComplete();
+        }
 
         /// <summary>
         /// 异步操作开始
@@ -31,6 +35,11 @@ namespace YooAsset
         /// </summary>
         protected abstract void OnAbort();
 
+        /// <summary>
+        /// 异步等待完成
+        /// </summary>
+        protected virtual void OnWaitForAsyncComplete() { }
+
         /// <summary>
         /// 异步操作系统是否繁忙
         /// </summary>