Prior to this commit, there was an attempt to remove extra data stored
at the Sculpt Undo `Node` level, specifically an extra position array
used when a deform modifier was in the stack.
The prior commit attempted to perform the undo step by calculating a
translation between the current positions and the previous unode
position and using that as the input to the deformation process.
However, this resulted in the undo not being completely applied to the
mesh and the data remaining in a weird state.
To fix this, this commit reintroduces some previously removed functions
and constructs to perform this restore step by swapping data if
necessary. We choose to not simply revert the change that applied this
as we want to eventually reinvestigate this path, but for the imminent
4.3 release, it makes more sense to restore previous behavior.
Pull Request: https://projects.blender.org/blender/blender/pulls/129496
aa937b1cab