display: Add a switch for variable refresh rate

This allows disabling and enabling variable refresh rate on monitors
that support it.
11 jobs for vrr-support in 7 minutes and 3 seconds (queued for 1 second)
latest
Status Name Job ID Coverage
  Build
passed build #655448

00:05:43

 
  Test
passed test #655449

00:01:20

 
  Manual
manual armv8 #655455
allowed to fail manual
manual asan #655451
allowed to fail manual
manual flatpak #655450
allowed to fail manual
manual msan #655454
allowed to fail manual
manual ppc64le #655456
allowed to fail manual
manual tsan #655452
allowed to fail manual
manual ubsan #655453
allowed to fail manual
 
  Review
manual review #655457
allowed to fail manual
manual stop_review #655458
allowed to fail manual