Mention ansible collections installed in Testing Farm

[psss]

Let users know which collections are available on the test runner.

Pull Request Checklist

• update the specification

[psss]

An old docs todo item. Blocked on Testing Farm having the docs published. Or are we ok with pointing directly to git?

[happz]

I’m not sure we should add TF-motivated caveats and notes into tmt metadata specification. It’s basically spoiling the information space with info good for a single special user of tmt. In other words, if - when… - MS picks tmt for their CI system, will we amend tmt specification to include pecularities of that system as well?

What would you say of we had a page dedicated to “Running tmt in TF”, collecting this kind of information? BTW, this is exactly the sort of info I would look for on TF website - what tmt version, what plugins, what collections can I use, and so on. Metadata specification does not feel like a good place for hosting this info.