Update vtkmCleanGrid to manage point and cell fields

The vtkmCleanGrid filter now supports all the features of the underlying Viskores clean grid filter. This includes the ability to merge coincident points and remove degenerate cells. It also correctly handles when point and cell fields would change size, which was not always handled correctly before.

This fixes an issue reported at https://discourse.paraview.org/t/mismatch-of-points-tuples-between-vtkmcleangrid-and-its-vtk-numpy-wrapper/17698.