Change: reworked the debug levels for network facility (#9251)

It now follows very simple rules:
0 - Fatal, user should know about this
1 - Error, but we are recovering
2 - Warning, wrong but okay if you don't know
3 - Info, information you might care about
4 -
5 - Debug #1 - High level debug messages
6 - Debug #2 - Low level debug messages
7 - Trace information

src/network/core/address.cpp

@@ -356,7 +356,7 @@ static SOCKET ListenLoopProc(addrinfo *runp)
 		DEBUG(net, 0, "Setting non-blocking mode failed: %s", NetworkError::GetLast().AsString());
 	}
 
-	DEBUG(net, 1, "Listening on %s", address.c_str());
+	DEBUG(net, 3, "Listening on %s", address.c_str());
 	return sock;
 }