waylandsink: Support xdg_shell stable
waylandsink currently only supports the ancient
wl_shell interface for window management, which was never intended to be used for anything real.
wl_shell is long since deprecated in favour of
xdg_shell, which has now been made stable and implemented across all of Mutter, QtCompositor, Weston, wlroots, and more: you can see the status of stable xdg_shell adoption also.
This involves using
xdg_wm_base as the replacement for
wl_shell, and a combination of
xdg_toplevel as a replacement for
xdg_shell allows far better negotiation of window size and state such as fullscreen, maximised, tiled, etc.