What this MR does / why does DuMux need it:
IntersectionEntitySet class we use the
cornersMatch function of raw intersection entities in order to detect geometrically identical intersections, for which we remove duplicates but define several neighbors of the target domain for a single intersection geometry. However,
cornersMatch expected the corners to be ordered identically, which is not necessarily the case, for instance, on surface grids. In 3d space, the intersection of a 2d geometry with two neighboring 3d geometries (in case the 2d geometry lies on the face between the two 3d geometries) can lead to differently ordered raw entities. In this case, the duplicates were not removed.