Codechange: use connection_string in favour of NetworkAddress (#9197)

We now resolve the connection_string to a NetworkAddress in a much
later state. This means there are fewer places constructing a NetworkAddress.

The main benefit of this is in later PRs that introduce different types
of NetworkAddresses. Storing this in things like NetworkGameList is
rather complex, especially as NetworkAddress has to be mutable at all
times.

Additionally, the NetworkAddress is a complex object to store simple
information: how to connect to this server.

src/network/core/tcp.h

@@ -77,7 +77,7 @@ protected:
 	NetworkAddress address;
 
 public:
-	TCPConnecter(const NetworkAddress &address);
+	TCPConnecter(const std::string &connection_string, uint16 default_port);
 	/** Silence the warnings */
 	virtual ~TCPConnecter() {}