Merge pull request #13969 from omoerbeek/rec-nod-threads

rec: use shared NOD (and/or UDR) DB, to avoid multiple copies in memory and on disk

diff --cc pdns/recursordist/pdns_recursor.cc
Simple merge

diff --cc pdns/recursordist/rec-main.cc
Simple merge

diff --cc pdns/recursordist/settings/table.py
Simple merge