hwc2: Switch vsync source to next active display

- Source vsyncs from next active display among builtin displays
  when primary display is powered off.
- Report back vsync timestamps as primary to the client.
- Source vsyncs back from primary display when the display is
  powered on again.

CRs-Fixed: 2200594
Change-Id: I453d7e19d982dadbfe5ff7b024a9ddc703578be3
6 files changed