refactor: try again to use getaddrinfo in announcer_udp (#4201)

libtransmission/session.h

@@ -31,7 +31,6 @@
 #include "bandwidth.h"
 #include "bitfield.h"
 #include "cache.h"
-#include "dns.h"
 #include "interned-string.h"
 #include "net.h" // tr_socket_t
 #include "open-files.h"
@@ -148,11 +147,6 @@ private:
             return tr_address::fromString(session_.announceIP());
         }
 
-        [[nodiscard]] libtransmission::Dns& dns() override
-        {
-            return *session_.dns_.get();
-        }
-
     private:
         tr_session& session_;
     };
@@ -1040,9 +1034,6 @@ private:
     // depends-on: session_thread_
     std::unique_ptr<libtransmission::TimerMaker> const timer_maker_;
 
-    // depends-on: event_base_
-    std::unique_ptr<libtransmission::Dns> const dns_;
-
     /// trivial type fields
 
     tr_session_settings settings_;
@@ -1149,7 +1140,7 @@ private:
     // depends-on: lpd_mediator_
     std::unique_ptr<tr_lpd> lpd_;
 
-    // depends-on: dns_, udp_core_
+    // depends-on: udp_core_
     AnnouncerUdpMediator announcer_udp_mediator_{ *this };
 
     // depends-on: timer_maker_, torrents_, peer_mgr_