ENH: add proximityRegions filter to distanceSurface (#2108)

- combines region-based and proximity-based filtering

  proxityRegions (post-filter):
    Checks the distance of the resulting faces against the original
    search surface. Filters based on the area-weighted distance
    of each topologically connected region.
    If the area-weighted distance of a region is greater than
    \c absProximity, the entire region is rejected.

STYLE: 'proxityFaces' as newer synonym for 'proximity' filter