Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3157>
This commits adds support for exporting xdg_surface handles via xdg_exporter and importing them via xdg_importer. This bumps the required wayland-protocols version to 1.6. https://bugzilla.gnome.org/show_bug.cgi?id=769786