xrt: Support XR_SESSION_STATE_LOSS_PENDING and XR_ERROR_SESSION_LOST
Adding xrt_multi_compositor_control::notify_surface_lose
so compositor can notify the client/session about surface lost (display disconnect) event. This would be translating to XR_SESSION_STATE_LOSS_PENDING
or XR_ERROR_SESSION_LOST
according to the time of event.
Verify with hello_xr and mock compositor event on Pixel 4/Motorola edge +.
Edited by Jarvis Huang