display-settings: Search for clonable modes only by resolution
`xfce_randr_clonable_mode()` must now return one mode per output,
because they are no longer the same modes (= resolution + refresh rate)
in general, only the resolutions are the same.
2 jobs for !84 with display-settings-clonable-modes in 2 minutes and 49 seconds
(queued for 2 seconds)