This adds a non-advertised wait_for_callback option in [EntityTransfer]. Default is always true.
Teleport tests disable the wait for callback from the destination region in order to run within a single thread.
This involves a large amount of change in test scene setup code to allow test scenes to share shared modules
SetupScene is now an instance method that requires an instantiation of SceneHelpers, though other SceneHelpers methods are still static
May split these out into separate classes in the future.
