reintroduce find subcommand and unify rev spec

[dhnasa]

the last symlink no longer exists, so we need another way to easily get the latest revision in external scripts

all subcommands (except restore) accept multiple revisions

Related issue(s): PL-131963

• Change is documented in changelog

Security implications

• Security requirements defined? (WHERE)

  • Principle of Defense in depth -> wrong matches can lead to accidentally removing unexpected/too many tags resulting in revisions being purged which shouldn't be
  • Fail securely -> providing invalid/malformed input will crash the program, parsing happens before actual actions happen

• Security requirements tested? (EVIDENCE)

  • added unit tests

[ctheune]

The security considerations are missing. We are processing user input here, are there implications?

Please update the PR template similar to fc-nixos to include the pointers for the security considerations.