Since we now moved the queuing of relayouts into the mapping and
unmapping functions, we no longer need to do it when adding or removing
a child, that's because removing a child always unmaps the child, and
adding it to a stage (if it's visible) will map it.
So remove those calls to queue_relayout() since they're no longer
needed.
With the above we no longer queue a relayout in
clutter_actor_add_child_internal(), that means there's one place where
we need to explicitely queue relayouts now: That's when using the
set_child_at_index/above/below() APIs, those are special because they
avoid unmapping and mapping of actors and would now no longer get a
relayout.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1366
29caa5bea5