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/core/tcp_content.h

@@ -21,8 +21,6 @@
 /** Base socket handler for all Content TCP sockets */
 class NetworkContentSocketHandler : public NetworkTCPSocketHandler {
 protected:
-	void CloseSocket();
-
 	bool ReceiveInvalidPacket(PacketContentType type);
 
 	/**