main: translate distro + release from run-time-dynamic defaults as well
    
    Tackling the debt mentioned in the previous commit, we factor out the
    translation logic into _resolve_dist function that is now called also
    for said detected defaults.   It also means that, for instance,
    autodetected Fedora Rawhide gets properly normalized to 27.999 version
    as of this commit, as filters using these raw values (not the best idea
    as likewise mentioned in the preceding commit) should only rely on
    normalized data if they really need to at all.
    
    Note that distribution names are assurably lower case already, but now
    also the detected default get alias-resolved for sure.
    
    Signed-off-by: Jan Pokorný <jpokorny@redhat.com>