message: udp: Add some log when session is deleted
  It is very helpful for debugging.
diff: @@ -179,6 +179,9 @@ UdpProxyFilter::ActiveSession::ActiveSession(ClusterInfo& cluster,
  }
  UdpProxyFilter::ActiveSession::~ActiveSession() {
  + ENVOY_LOG(debug, "deleting the session: downstream={} local={} upstream={}",
  + addresses_.peer_->asStringView(), addresses_.local_->asStringView(),
  + host_->address()->asStringView());
  cluster_.filter_.config_->stats().downstream_sess_active_.dec();
  cluster_.cluster_.info()
  ->resourceManager(Upstream::ResourcePriority::Default)
  