loader: Add infrastructure for tracking active CRTC resources
This provides a cached view of the current screen resources, with the coordinates and refresh rate for every active CRTC. It's currently only implemented for X11/XCB. Fixes: 47526556 ("egl/x11: implement ANGLE_sync_control_rate") Reviewed-by:Adam Jackson <ajax@redhat.com> Part-of: <mesa/mesa!20665>