In case the user has just the one display but they don't want to show it
in their main workspace when sharing video, allow creating a virtual
display.
This also will allow using remote devices as support displays.
DrmGpu::updateOutputs is now changing the state of some drm properties
without changing the fitting output state (namely RenderLoop inhibition)
which can lead to rendering being inhibited indefinitely in some cases
IN_FORMATS contains information about which buffer formats can be
scanned out with a given drm plane. Using these plane-specific
format+modifier combinations as well as explicit modifiers in
general can yield bandwidth and performance improvements,
especially in multi-gpu systems.
When the last output gets disconnected, create a virtual output as a
placeholder until we have access to a physical output again. While
this placecholder never gets rendered to, with virtual outputs in
general that is possible (with gbm and qpainter atm) and can be done
for future use cases like wireless displays.
CCBUG: 420160
CCBUG: 438839
