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

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