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/network_gamelist.cpp

@@ -112,7 +112,6 @@ void NetworkGameListRemoveItem(NetworkGameList *remove)
 			ClearGRFConfigList(&remove->info.grfconfig);
 			delete remove;
 
-			DEBUG(net, 4, "[gamelist] removed server from list");
 			NetworkRebuildHostList();
 			UpdateNetworkGameWindow();
 			return;