AssetManager does not correctly call delegates if bShouldUseSynchronousLoad is true

There's a bug in UAssetManager::LoadAssetList where the passed in DelegateToCall is not being called in the bShouldUseSynchronousLoad case. This can cause gameplay logic to fail when that bool is true.

It's only true by default when doing something like cooking, but games can override it to be true in other cases. The fix is to properly call the delegate

1. Create an asset manager subclass (like RPGAssetManager) and set bShouldUseSynchronousLoad to true
2. Call LoadAssetList (or any related function like PreloadPrimaryAssets) and pass in a StreamableDelegate
3. The passed in streamable delegate will not get called