This code will be poked exclusively from the MetaWindowDrag, so change the API to start passing this object around. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2683>
This is now something that is mainly handled from the compositor side, so it makes sense to move it there. Following commits will cut all ties with src/core. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2683>