More compact horizontals

[Lol3rrr]

Currently all horizontal lines are put on their own y-height. This is obviously the easiest solution, but can result in unnecessarily large Graphs, to combat this we should attempt to compact these horizontals by putting multiple of them on the same y-height when they don't intersect with each other. We don't need to find the perfect solution in every case and should just do it on a best effort basis, but I think this might make things more compact without too much overhead or cost.