resolved: gracefully handle with packets with too large RR count

Apparently, there are plenty routers in place that report an incorrect
RR count in the packets: they declare more RRs than are actually
included.

Let's accept these responses, but let's downgrade them to baseline, i.e.
let's suppress OPT in this case: if they don't even get the RR count
right, let's operate on the absolute baseline, and not bother with
anything fancier such as EDNS.

Prompted-by: https://github.com/systemd/systemd/issues/12841#issuecomment-724063973

Fixes: #3980
Most likely fixes: #12841

(cherry picked from commit 18674159)