Check indices with CellSetExtrude reverse look up

Previously, the check for visit points with cells for `CellSetExtrude`
only looked at the count of incident cells. This expands the check to
make sure that it actually returns the expected cells.
6 jobs for scatter-extrude-cells in 0 seconds (queued for 1 second)
Status Name Job ID Coverage
  External
passed cdash-buildbot

passed vtk-m-dragnipur-osx-shared-debug+32bit_ids+64bit_coords+clang+tbb

00:12:35

passed vtk-m-dragnipur-osx-static-release+64bit_coords+clang+tbb

00:00:23

passed vtk-m-osheim-windows-shared-debug+ninja-vs-2017+tbb

00:25:59

passed vtk-m-osheim-windows-static-release+ninja-vs-2017+tbb

00:02:20

passed cdash-buildbot