Problem: actions/checkout@v7 refuses to checkout fork pull request code
on `pull_request_target` trigger, breaking backport and reviewers-remove
workflows on external PRs.
Solution:
* backport: Checkout the merged-into base branch by name.
* reviewers-remove: inline script so no checkout needed.
- Simplify some workflow steps and auxiliary scripts
- Build library using cmake when not cross-compiling
- Try to fetch fixtures from cache first
- Use `actions-rust-lang/setup-rust-toolchain`
It's basically a bot that closes issues or PRs if the author hasn't
responded after 30 days. This is only done on issues/PRs that has the
`more-information-needed` label and is meant to be used for issues that
has hit a dead-end and cannot progress without further information from
the author. If the author responds after an issue is closed and gives
more context the issue can simply be reopened.
