Substantial elements following a divot should be at least as far in each
cardinal direction from the origin point in order to be considered
substantial. This catches cases where the "substantial" element is
actually a straight segment away from the divot
Fixes https://gitlab.com/kicad/code/kicad/issues/14130
Fractured polygons are always fractured along the x-axis, so when
checking to see if a segment is a fracture point, we check if the y
coordinate is equal. This avoids situations where there are multiple
fracture points between two inflection points
Additionally, we add a second check to ensure we don't hit spurious
blobs (all kinks should be symmetric and therefore be substantial in
each direction)
Fixes https://gitlab.com/kicad/code/kicad/issues/14130
Seth Hillbrand