rust: add logging utils This change adds the `log` crate, the community-approved logging facade backed by Rust core developers as well as the logging-consumer crate `simple_logger` to build a foundation for logging from Rust. Using this setup allows us to choose how to log depending on the way `hg-core` is used: if it's within the context of `hg-cpython`, we might not want to use it the same way as with a direct cli for example. Differential Revision: https://phab.mercurial-scm.org/D8252

rust-status: traverse working directory in parallel Using `rayon` for this task ensures that we are using the same work-stealing threadpool for everything. This change introduces `crossbeam` as an explicit dependency, although it is already a dependency of `rayon`. It provides better structures for multi-threaded tasks than the stdlib. Differential Revision: https://phab.mercurial-scm.org/D8251

rust-status: wrap `stat_dmap_entries` to ease profiling Differential Revision: https://phab.mercurial-scm.org/D8250

rust-status: refactor handling of unknown files Differential Revision: https://phab.mercurial-scm.org/D8249

rust-status: move to recursive traversal to prepare for parallel traversal I have looked into traversing the working directory in parallel either by a recursive or an iterative algorithm. The recursive approach won quite decisively both in terms of performance and code readability. You can look at my experiment here: https://heptapod.octobus.net/Alphare/rayon-recursive-traversal The chance of a stack overflow happening because the directories get too nested seems slim. This change does not yet do anything in parallel. Differential Revision: https://phab.mercurial-scm.org/D8215

rust-pathauditor: use interior mutability for use in multi-threaded contexts The usual recommendation for using `RwLock` or `Mutex` is that if there are about as many write as there are reads, use `Mutex`, and if there are more reads than writes, use `RwLock`. If after the main bottleneck (i.e. parallel traversal) is removed this shows up on profiles, we should investigate using the `parking_lot` since we don't need a poisoning API, or maybe move to different types of caches entirely. Differential Revision: https://phab.mercurial-scm.org/D8213