rust-filepatterns: use bytes instead of String In my initial patch, I introduced an unnecessary hard constraint on UTF-8 filenames and patterns which I forgot to remove. Although the performance penalty for using String might be negligible, we don't want to break compatibility with non-UTF-8 encodings for no reason. Moreover, this change allows for a cleaner Rust core API. This patch introduces a new utils module that is used with this fix. Finally, PatternError was not put inside the Python module generated by Rust, which would have raised a NameError. Differential Revision: https://phab.mercurial-scm.org/D6485