Merge pull request #6191 from rgacogne/dnsdist-rings-sharding

dnsdist: Ring buffers sharding

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

diff --cc pdns/dnsdist.cc
Simple merge

diff --cc pdns/dnsdist.hh
Simple merge

diff --cc pdns/dnsdistdist/docs/reference/config.rst
Simple merge