relnotes: write final 6.9 notes I've folded bugfixes that only exist to fix 6.9-specific things to the best of my attention span for this task.

rust: add some warning about using Rust I hope this is not too scary, but as discussed last month, we need to have a better compatibility story before pushing more people toward Rust.

rust: update install instruction As discussed last Friday after publishing the rc wheel, we need to update the rust readme and highlight that change in the release announcement if we want people using Rust to keep being able to use pip.

ci: add sink for wheels too Sight.

wheel: also build wheel for linux arm64 in the CI We don't test them yet, but we build them, as as many other flavors.

contrib: add a script to build all of the wheels on macOS This is mostly a translation of `contrib/packaging/build-windows-wheels.bat`, except the default pythons to build can be inferred from `setup.py` and/or `pyproject.toml`, and all use the same configuration. All we need to do is force the building of translation files, tell it to skip pypy wheels, and tell it to build universal2 wheels instead of for the current architecture.

rhg-status: rename a variable to be more explicit Possibly we would have caught the looming bug earlier if this had been named closer to what it actual is used for.