add caching to most type folders, rm region uniquification Fixes the new minimization of the hang in nalgebra and nalgebra itself :3 this is a bit iffy, especially the cache in `TypeRelating`. I believe all the caches are correct, but it definitely adds some non-local complexity in places. The first commit removes region uniquification, reintroducing the ICE from https://github.com/rust-lang/trait-system-refactor-initiative/issues/27. This does not affect coherence and I would like to fix this by introducing OR-region constraints r? `@compiler-errors`