stable/xdg_shell: clarify 'must be in response'

Make it clear that the serials of the latest presses must much the ones passed in move, resize, grab, and show_window_menu.

Add a note that that you may want to delay the sending of these requests to avoid false positives when the users intend to do double/triple clicks. At least triggering of xdg_toplevel::move after right after click on CSD header was found common.

Signed-off-by: Kirill Chibisov contact@kchibisov.com Links: https://gitlab.gnome.org/GNOME/mutter/-/issues/2669