Add: [Network] Keep the refresh button in lowered state while refreshing (#9600)

This gives user visual feedback that the refresh is still pending, and
prevents people from clicking again and again thinking nothing is
happening. This is especially true for connections that fall back to
TURN, as that takes a few seconds to kick in.

Additionally, prevent clicking on the button again while a refresh
is pending. This is only delaying a successful result.

src/network/network.cpp

@@ -635,6 +635,7 @@ public:
 	{
 		NetworkGameList *item = NetworkGameListAddItem(connection_string);
 		item->status = NGLS_OFFLINE;
+		item->refreshing = false;
 
 		UpdateNetworkGameWindow();
 	}
@@ -653,6 +654,10 @@ void NetworkQueryServer(const std::string &connection_string)
 {
 	if (!_network_available) return;
 
+	/* Mark the entry as refreshing, so the GUI can show the refresh is pending. */
+	NetworkGameList *item = NetworkGameListAddItem(connection_string);
+	item->refreshing = true;
+
 	new TCPQueryConnecter(connection_string);
 }