[Maintenance] performance audit of polyhedra operations

[tesseralis]

My current performance metric is "look at how fast the test suite runs". In my defense, it is pretty thorough -- it runs every possible operation on every possible polyhedron with every possible option.

Right now, my metric for performance is "gut check". "oh this looks like it'll be expensive to calculate -- MEMOIZE". "oh I'm creating a bunch of intermediate objects -- BUILDERS".

I also can't figure out how to use a non-browser profiler for JS.

If anyone wants to test out their perf chops and get my test suite down from 10s to like, 8s, be my guest!