b21294dcac
This are called when a clone directly attaches to an actor. While not reliable to know whether a particular actor is cloned or not, one can at least this way get notified about whether an actor in particular is cloned. This can be useful for e.g. the MetaWindowActor, as it's what's most likely cloned, e.g. for alt-tab views etc. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3019>