Blender Git Loki

Fix T75743: Implement restore for brushes that modify their own data

This implements the restore function for Draw Face Sets and Layer, which
don't affect coordinates or masks directly. This is needed for the
anchored and dot brush strokes.

Layer frees the current displacement and a new one is created on each
stroke sample. Draw Face Sets copies the data back from the first undo
node to the mesh datalayer.

Also fixes T75727

Reviewed By: jbakker

Maniphest Tasks: T75727

Differential Revision: https://developer.blender.org/D7442