* CI: upgrade macOS runner to version 12 (Monterey)
* CI: upgrade actions/checkout to v3
* CI: remove retry logic for apt
The Linux runners on GitHub Actions already retries up to 10 times,
see:
6c93c24107/images/linux/scripts/base/apt.sh (L11-L12)
* CI: remove redundant `DEBIAN_FRONTEND=noninteractive` env
The Linux runners on GitHub Actions already sets this env variable,
see:
6c93c24107/images/linux/scripts/installers/dpkg-config.sh (L10)
* CI: remove redundant `HOMEBREW_NO_AUTO_UPDATE=1` env
The macOS runners on GitHub Actions already sets this env variable,
see:
6c93c24107/images/macos/provision/configuration/environment/bashrc (L26)
* CI: prefer shorthand flag of apt-get `--fix-missing`
* CI: install libjxl on macOS runner
* Update test suite's README.md
