Refactor RTSP handling to be session-based rather than socket-based

This is required to support per-session attributes like encryption keys during RTSP message processing.

src/stream.cpp

@@ -411,6 +411,8 @@ namespace stream {
       safe::mail_raw_t::event_t<video::hdr_info_t> hdr_queue;
     } control;
 
+    std::uint32_t launch_session_id;
+
     safe::mail_raw_t::event_t<bool> shutdown_event;
     safe::signal_t controlEnd;
 
@@ -523,6 +525,9 @@ namespace stream {
         }
       }
 
+      // Once the control stream connection is established, RTSP session state can be torn down
+      rtsp_stream::launch_session_clear(session_p->launch_session_id);
+
       session_p->control.peer = peer;
 
       // Use the local address from the control connection as the source address
@@ -1881,6 +1886,7 @@ namespace stream {
       auto mail = std::make_shared<safe::mail_raw_t>();
 
       session->shutdown_event = mail->event<bool>(mail::shutdown);
+      session->launch_session_id = launch_session.id;
 
       session->config = config;