We have a replacement in ClutterActor, now.

The old ClutterContainer API needs to be deprecated, and the raise() and
lower() virtual functions need a default implementation, so we can check
for implementations overriding them, by using the diagnostic mode like
we do for add(), remove(), and foreach().

The sort_depth_order() virtual function just doesn't do anything, as it
should have been made ages ago.

The Actor wrappers for the Container methods also need to be deprecated.