Use pre configure mechanism for window positioning #2216
Description
https://mutter.gnome.org/meta/signal.Window.configure.html
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4076
This can be used in the windowpositioner: we only change the values of the given MetaWindowConfig and it will be applied.
Unfortunately this is OS9 material because it requires a more recent mutter version