MountCameraFix

This tweaks EntityAgent.doMount to be idempotent to fix the issue of the camera resetting orientation when on a vehicle/mount when a full attibrute resync occurs.

 

<span style="text-decoration: line-through;">Also, this increases the threshold of dirtied attributes before a full resync occurs. This may negatively impact gameplay on higher-latency connections.</span>

Use Rubberbandaid or HoD to increase the attribute resync threshold going forward.

Tested against 1.20.10-1.21.5