Draft: (Re)move Xwayland related protocols

Remove the Xwayland specific protocols to move them to Xwayland itself.

This helps unclutter the Wayland protocols by moving application specific protocols out of wayland-protocols.

⚠ Important: This MR should not be considered before its counterpart in Xwayland (xorg/xserver!1194 (closed)) has been merged and is part of a stable release of Xwayland. This is mostly an RFC for now, to see what people think of that.