Port display settings to Wayland
This MR also ensures that the other components of xfce4-settings run on Wayland if possible and are disabled if not, but the only real port to Wayland concerns the display settings, as these are the only ones for which there is a protocol that allows this as far as I know: https://wayland.app/protocols/wlr-output-management-unstable-v1.
Edited by Gaël Bonithon