add "different_gpu" reporting from driver

Add capability for a driver to request winsys to start different_gpu triggered
drawable shadowing scheme.
Add flag to virgl to report different_gpu flag to guest.
Add flag to pipe config for driver to report it.
Add DRI query to report it.
160 jobs for !11275 with different_gpu in 9 seconds (queued for 8 seconds)
latest merge request