Overlap detection & removal primitives

[RickyDaMa]

This PR adds functions to concatenate BezPaths, as well as functions that use linesweeper to perform overlap removal & detection. In future PRs these can then be used to do overlap removal for statics (#717) and automatically set the overlap bit (#2061).

Outstanding questions:

1. Do we want to expose linesweeper types internally within the fontc crates? Currently linesweeper::Error is exposed.
2. Do we need to specify an epsilon value ourselves? linesweeper uses 1e-6 by default.
3. Is this code living in the right place? I can foresee fontir needing the overlap removal method and fontbe needing overlap detection, so my rationale was that the logic should go in the "general utilities & types" crate.
4. What sort of QA do we want around this code to be satisfied that it's doing the right thing? Tests are pretty minimal right now while this is a proof of concept, but when it comes to actually setting the overlap bit and such we probably want to be a lot more rigorous

For the TODOs in code that talk about potential linesweeper features, I have opened an issue and a PR.

[anthrotype]

Wait, shouldn't the logic be flipped here?

-        .all(|(non_zero_contour, even_odd_contour)| non_zero_contour.path == even_odd_contour.path);
+        .any(|(non_zero_contour, even_odd_contour)| non_zero_contour.path != even_odd_contour.path);

[RickyDaMa]

Shoot sorry, forgot to push my latest before opening the PR 🙈 This expression ended up getting refactored, but should be semantically correct now