rename: queries.Query -> query.Query. queries.Subject -> subject.Subject.

The 'queries' name was confusing as there's only one Query class in there
and Subject is not a Query. This technically constitutes an apichange: the
old module was referenced in the documentation. That's why the dnf.queries
stays for now as a deprecated module.
Add the "determining the fastest mirror" feedback

XXX: This was originally a method of LibrepoCallbackAdaptor class,
but we probably don't want librepo symbols used in dnf.cli.progress.
The inlined callback is much simpler anyway. Needs new librepo.