Hide "External Only" and "Built-in Only" options in monitor switcher when there is no built-in monitor
In gnome-control-center#422 (closed) a user (@hogar1977) identified the issue that the monitor layout switcher will always show all options, even if these options are not possible.
We should at least hide the External Only/Built-in Only options when the user is on a desktop and there is no built-in display.
Also, one could probably argue that switching between single/join only makes sense if there is a buildin display (i.e. we could define "single" as "built-in only"); that would effectively result in the switcher being disabled on desktop hardware.
Edited by Benjamin Berg