Codechange: [Network] split CloseSocket and CloseConnection more clearly (#9261)

* Codechange: [Network] split CloseSocket and CloseConnection more clearly

- CloseSocket now closes the actual OS socket.
- CloseConnection frees up the resources to just before CloseSocket.
- dtors call CloseSocket / CloseConnection where needed.

src/network/network_content_gui.cpp

@@ -260,7 +260,7 @@ public:
 	{
 		if (widget == WID_NCDS_CANCELOK) {
 			if (this->downloaded_bytes != this->total_bytes) {
-				_network_content_client.Close();
+				_network_content_client.CloseConnection();
 				delete this;
 			} else {
 				/* If downloading succeeded, close the online content window. This will close