Investigate `lox` as an alternative to `HalfEdgeMesh`

[setzer22]

The recently released lox crate looks like a fast and usable library for geometry processing that could potentially replace the custom HalfEdgeMesh in blackjack 👀

One particular similarity between the two data structure is the fact lox contains a concept of "mapping" that is very close in spirit to blackjack's channels. Something important to explore there would be to see how an existing library fits into the more flexible borrowing patterns provided by blackjack (i.e. channels have interior mutability and, optionally, shared ownership).