Handling not-working output configurations better
!844 (merged) makes all the configurations work that are possible on hotplug but it's not solving the complete problem. If we can't drive all the outputs a message should be shown in KScreen, maybe a notification, too.
We should also list outputs that we can't drive at the moment in KScreen, and try to re-allocate CRTCs whenever the user configuration changes and it doesn't work. An example for that would be when we have 3 CRTCs (Intel iGPU) but 4 outputs. Switching between which 3 outputs you want to use should work