Add argument to allow configuring whether to combine result segments in `pairwise_linestring_intersection`

[isVoid]

According to @thomcom, contains fails with the following use case:

from shapely.geometry import LineString
l1 = LineString([(0, 0), (0.25, 0), (0.75, 0), (1, 0)])
l2 = LineString([(0, 0), (1, 0)])
print(l1.contains(l2))
print(l2.contains(l1))

The number of vertices differs currently for both inputs, because pairwise_linestring_intersection merges the result for both cases and in the code path, there's no way distinguishing them.