rust: run `cargo clippy`
These automatic fixes are good to have because they make the code
more idiomatic and less surprising.
The transform from `sort` -> `sort_unstable` is questionable, but this is
only in a test, so it doesn't matter in our case.
# Files that just need to be migrated to the formatter.
# Do not add new files here!
mercurial/cext/manifest.c
mercurial/cext/osutil.c
# Vendored code that we should never format:
syntax: glob
contrib/python-zstandard/**.c
contrib/python-zstandard/**.h
hgext/fsmonitor/pywatchman/**.c
mercurial/thirdparty/**.c
mercurial/thirdparty/**.h
mercurial/pythoncapi_compat.h