vtkPVGhostCellsGenerator: smart Partitioned composite distribution
For composite structures containing both HTG and non HTG types, the PV GCG would transform the input data structure into a PartitionedDataSetCollection. We now properly iterate over the composite structure, grouping Partitioned Datasets toghether and routing them to the right GCG filter.
Requires vtk/vtk!11912 (merged)