Tweak vtkContourTriangulator tolerances
The polygon bounds check didn't include a tolerance, so roundoff error in point interpolation could cause poly-in-poly checks to fail when they should have succeeded. This was specifically causing failures in vtkClipClosedSurface when the generated polys had normals along X, Y, or Z since the polygon bounds were vanishingly thin along the normal direction.
For more info, see "vtkClipClosedSurface bad result" thread on VTK discourse.
Backport: release
Edited by David Gobbi