support legacy dependency mode

YOOASSET_LEGACY_DEPENDENCY

Assets/YooAsset/Runtime/ResourceManager/Operation/Internal/LoadBundleFileOperation.cs

@@ -153,7 +153,23 @@ namespace YooAsset
             if (IsDone == false)
                 return false;
 
-            return RefCount <= 0;
+            if (RefCount > 0)
+                return false;
+
+            #region YOOASSET_LEGACY_DEPENDENCY
+            // 检查引用链上的资源包是否已经全部销毁
+            // 注意：互相引用的资源包无法卸载！
+            if (LoadBundleInfo.Bundle.ReferenceBundleIDs.Length > 0)
+            {
+                foreach (var bundleID in LoadBundleInfo.Bundle.ReferenceBundleIDs)
+                {
+                    if (_resourceManager.CheckBundleDestroyed(bundleID) == false)
+                        return false;
+                }
+            }
+            #endregion
+
+            return true;
         }
 
         /// <summary>