Try to fix some issues show in
#17404 as well as
other transparency issues with vtkCompositePolyDataMapper2

Previously mappers could only report GetIsOpaque which would render them
as opaque or transparent. With this change mappers can report if they
have TranslucentPolygonalGeometry as well as OpaqueGeometry and they can
report both. If they report both they will get invoked on both passes.
This allows complex mapperssuch as CPDM2 to do render some blocks during
the opaque pass and other blocks during the translucent pass.

Create better logic in vtkScalarsToColors to report If the scalar
mapping would produce translucent results and use that logic in a couple
places where it had been duplicated.