Fix all lints

[JoeyBF]

It's been a few months so there were a few new lints to fix. Most importantly:

• OooTracker is now a BTreeSet instead of a Box<BTreeSet>. This shouldn't make a difference since a BTreeSet is already heap-allocated.
• PPart is now u32, no longer either u16 or u32 depending on features. This solves the numerous superfluous cast lints that clippy was upset about, and benchmarking shows that there is no measurable hit in performance.

[JoeyBF]

See rayon-rs/rayon#952 for the miri test failure

[JoeyBF]

110 fixes miri