Merge pull request #10338 from rgacogne/ddist-downstream-tls

dnsdist: Implement cross-protocol queries

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

diff --cc pdns/dnsdistdist/tcpiohandler-mplexer.hh
Simple merge

diff --cc pdns/dnsdistdist/test-dnsdisttcp_cc.cc
Simple merge

diff --cc pdns/tcpiohandler.cc
Simple merge

diff --cc pdns/tcpiohandler.hh
Simple merge