isoSurfaceCell with planes exactly through points is not detected

Run compressible/rhoSimpleFoam/squareBend with attached

samplingDebug

it will produce lots of missing triangle. This is due to the pre-filtering of potentially cut cells. You can make it work by having calcCutType always returns CUT. The issue turns up with the distanceSurface where you use an exact distance 0. We only check for some vertices (e.g. of an edge) above and some below, not for both exactly on.