wayland: support presentation-time version 2
The difference between version 1 and version 2 is what to report back for the refresh rate in VRR. Technically, version 1 required sending a refresh rate of 0 for variable refresh rate which mutter wasn't previously doing. It always sent the refresh rate of the crtc which is what version 2 requires. Fix this checking the mode during the presentation event and setting 0 if we have vrr and version 1 of presentation time.