fix(UI): 修正卸载UI资源时实例销毁顺序问题

在卸载UI资源时，先销毁UI实例再进行资源卸载，避免资源引用未释放的问题。对于非Bundle资源，使用UnloadUnusedAssets确保资源完全释放。

Author: AlianBlank

Runtime/UGUIFormHelper.cs

@@ -182,16 +182,15 @@ public override void ReleaseUIForm(object uiFormAsset, object uiFormInstance, ob
                 return;
             }
 
+            Destroy((Object)uiFormInstance);
             if (uiFormAssetPath.IndexOf(Utility.Asset.Path.BundlesDirectoryName, StringComparison.OrdinalIgnoreCase) >= 0)
             {
                 m_AssetComponent.UnloadAsset(uiFormAssetPath);
             }
             else
             {
-                UnityEngine.Resources.UnloadAsset((Object)uiFormInstance);
+                UnityEngine.Resources.UnloadUnusedAssets();
             }
-
-            Destroy((Object)uiFormInstance);
         }
 
         [UnityEngine.Scripting.Preserve]