AssetBundleUnloadOperation Asynchronous unload request for an AssetBundle.
卸载捆绑包中的资源。
When unloadAllLoadedObjects is false, tracking data structures and any memory buffers holding content of the AssetBundle will be freed. But any instances of objects loaded from this bundle will remain intact.
当 unloadAllLoadedObjects 为 true 时，也将销毁从该捆绑包加载的所有对象。如果场景中有 GameObjects 引用这些资源，则对它们的引用将丢失。
After calling UnloadAsync on an AssetBundle, you cannot load any more objects from that bundle and other operations on the bundle will throw InvalidOperationException.
Additional resources: UnloadAllAssetBundles, Unload, Using AssetBundles Natively.