Deprecate vtkInteractorStyleMPRSlice and use VolumeMapper's clipping planes instead.

[aylward]

Is your feature request related to a problem? Please describe.

vtkInteractorStyleMPRSlice is incompatible with DistanceWidget and other features

Describe the solution you'd like

Replace with Volume Mapper's clipping plance

Describe alternatives you've considered

None

Additional context

N/A

[agirault]

Nice! I totally agree. My understanding is that the contributors created vtkInteractorStyleMPRSlice because they have to use the camera clipping planes to get a slab of the VolumeMapper, so the camera needs to be adjusted to create the slice.

That means that we should be able to just use the VolumeMapper if add support for clipping planes to the mapper: then we don't depend on the camera and we are not restricted to an interactor (i.e.: more of a Rendering improvement feature). @floryst please correct me if I got that wrong.

#1720 (comment) (labeled Hall of Fame 👑 by Seb!) has an interesting discussion on the VolumeMapper, and how it relates to the ImageMapper for slicing along an axis not aligned with the volume. I think it's relevant to read, though there might be some confusion regarding what "clip planes" are used/exist (camera vs mapper), which we just need to clarify.