Draft: wayland/xdg-shell: Add support for xdg_toplevel edge constraints
They extend the tiling capabilities of xdg-shell by communicating when a window cannot be resized from a specific edge, e.g. because it's next to a monitor edge.
It is roughly equivalent to the gtk_surface1 edge constraint enum.
Implementation for https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/230