dnsdist-1.9.x: Backport of #14768 - setTicketsKeyAddedHook: pass a std::string to the hook to avoid luawrapper to truncate content at potential null chars

dnsdist-1.9.x: Backport of #14768 - setTicketsKeyAddedHook: pass a std::string to the hook to avoid luawrapper to truncate content at potential null chars #10481