wayland: Change backend api to use GdkToplevel
Most of the surface api we have in the Wayland backend only makes sense for toplevels, so reshuffle things to take a GdkToplevel instead of a GdkSurface.
Update all callers and the docs.
Most of the surface api we have in the Wayland backend only makes sense for toplevels, so reshuffle things to take a GdkToplevel instead of a GdkSurface.
Update all callers and the docs.