Blender Git Loki

Stop dyntopo updates from happening in masked areas

Fixes [#34348] Collapse short edges affects masked geometry
/projects.blender.org/tracker/?func=detail&aid=34348&group_id=9&atid=498

Fixed by disallowing topology updates on edges with a vertex masked at
50% or greater. This is a necessarily arbitrary choice; can't do
halfway updates for topology like we can with displacement.