While moving to a prescribed dependencies in MDEV-28011, an error was made
in the merge. The Ubuntu and Debian supported architectures of rocksdb-tools
are different and need to be treated as such.

This actually had no effect as our support of mariadb-plugin-rocksdb was never
different to the distro support of rocksdb-tools. Some notes where added
to this affect.

There is also nothing to do for Debian sid, and never should be.

The differentiation and grouping of distro codenames is for convenience in
merging upwards as more dependencies change across distro versions.

The fixing of versions rather than relying on apt-cache to be correct prevents
unstable changes between releases, and potentially uninstallable packages like
happened in MDEV-28014.

Correct comment about zstd to MDEV-16525