Turbopack: Use `Path`/`PathBuf` for all of the invalidation logic (#82132)
Common convention in our codebase is that `Path`/`PathBuf` are used for raw OS-level paths, and `RcStr` is used for normalized paths exposed by `turbo_tasks_fs`.
These are raw OS paths, so we should use `Path`/`PathBuf`.
This has some benefits in that it makes the implementation of https://github.com/vercel/next.js/pull/82133 easier, because `Path`'s `Ord` implementation is better for our use-case.