Add rage to bookworm image (deb version)

Testing recovery bundles in swh-alter requires rage and rage-keygen. See: https://github.com/str4d/rage/blob/main/rage/Cargo.toml

The author provides a pre-built Debian package on GitHub upon release. We now install its dependency, fetch the package and use dpkg to add it to the system.

See !64 (merged) for another implementation using cargo instead.