Dependency version messages

[mattias-p]

Today we include a number of DEPENDENCY_VERSION messages in the results.
Some of these affect Engine's behavior with regard to its testing and some don't.
This set should be updated to also include all depenedencies that affect Engine's behavior with regard to testing, and only those.

Examples of dependencies that affect testing behavior:

• Zonemaster::LDNS
• ldns

Most or all of the other dependencies we currently emit DEPENDENCY_VERSION today do not affect testing behavior and should be removed.