Merge pull request #14339 from rgacogne/ddist19-backport-14302

dnsdist-1.9.x: Backport of 14302: Add Lua FFI bindings to generate SVC responses

diff --cc pdns/dnsdistdist/dnsdist-lua-ffi-interface.h
Simple merge

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

diff --cc pdns/dnsdistdist/test-dnsdist-lua-ffi.cc
Simple merge