update operation system

Operation状态增加Processing处理中状态

Assets/YooAsset/Runtime/OperationSystem/AsyncOperationBase.cs

@@ -73,13 +73,18 @@ namespace YooAsset
 
 		internal abstract void Start();
 		internal abstract void Update();
-		internal void Finish()
+
+		internal void OnFinish()
 		{
 			Progress = 1f;
 			_callback?.Invoke(this);
 			if (_taskCompletionSource != null)
 				_taskCompletionSource.TrySetResult(null);
 		}
+		internal void OnStart()
+		{
+			Status = EOperationStatus.Processing;
+		}
 
 		/// <summary>
 		/// 清空完成回调