Blender Git Loki

Update viewport rotation origin when changing Face Set visibility

Small UX fix. When hidding everything but the active face set with H,
the last stroke lotation center can be in a part of the model that is
hidden, so viewport navigation becomes confusing until you start a new
stroke on the visible face set. Now the viewport navigation rotation
center is updated to the active vertex when using a visibility operation
that uses it, so it always rotates using the visible face set as the
origin.

Reviewed By: jbakker

Differential Revision: https://developer.blender.org/D7137