Merge pull request #4788 from rgacogne/dnsdist-cache-hit-rules

dnsdist: Add cache hit response rules

diff --cc pdns/README-dnsdist.md
Simple merge

diff --cc pdns/dnsdist-console.cc
Simple merge

diff --cc pdns/dnsdist-lua.cc
Simple merge

diff --cc pdns/dnsdist-lua2.cc
Simple merge

diff --cc pdns/dnsdist-tcp.cc
Simple merge

diff --cc pdns/dnsdist.cc
Simple merge

diff --cc pdns/dnsdist.hh
Simple merge