Improve construction speed

[JayKickliter]

Major goal: it would be awesome it we could both construct a compacted tree and drain it to a vec faster than calling libh3's compact() function. My gut feeling is the bottle neck currently lays non-deterministic alloction of behavior of a hexset. I do have a PR that improves things, but it probably needs some work. See https://github.com/JayKickliter/HexSet/pull/4