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
(cherry picked from commit 7653a2bf99)
