Merge pull request #10047 from rgacogne/rec-aggressive-nsec-caching

rec: Implement rfc 8198 - Aggressive Use of DNSSEC-Validated Cache

diff --cc pdns/pdns_recursor.cc
Simple merge

diff --cc pdns/rec_channel_rec.cc
Simple merge

diff --cc pdns/recursordist/Makefile.am
Simple merge

diff --cc pdns/recursordist/docs/metrics.rst
Simple merge

diff --cc pdns/recursordist/docs/settings.rst
Simple merge

diff --cc pdns/recursordist/test-syncres_cc.cc
Simple merge

diff --cc pdns/syncres.cc
Simple merge