This implements the new 'bounds' event that is part of the xdg_toplevel
interface in the xdg-shell protocol. It aims to let clients create
"good" default window sizes that depends on e.g. the resolution of the
monitor the window will be mapped on, whether there are panels taking up
space, and things like that.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2167>
