Write a file `uuid` in server's data directory that contains random UUID, generated at startup if file does not exist.

It will be used for several purposes:
- to anonymously identify server in Sentry (currently Sentry is unusable);
- (possible future usage) to identify server in ensemble.

@tavplubix comments?
{
                Poco::Net::ServerSocket socket;
                auto address = socketBindListen(socket, listen_host, port);
                socket.setReceiveTimeout(settings.receive_timeout);
                socket.setSendTimeout(settings.send_timeout);
                servers->emplace_back(port_name, std::make_unique<Poco::Net::TCPServer>(
                    new TCPHandlerFactory(*this,  false,  false),
                    server_pool,
                    socket,
                    new Poco::Net::TCPServerParams));
                LOG_INFO(log, "Listening for connections with native protocol (tcp): {}", address.toString());
            });
            
            port_name = "tcp_with_proxy_port";
            createServer(listen_host, port_name, listen_try, [&](UInt16 port)
            {
                Poco::Net::ServerSocket socket;
                auto address = socketBindListen(socket, listen_host, port);
                socket.setReceiveTimeout(settings.receive_timeout);
                socket.setSendTimeout(settings.send_timeout);
                servers->emplace_back(port_name, std::make_unique<Poco::Net::TCPServer>(
                    new TCPHandlerFactory(*this,  false,  true),
                    server_pool,
                    socket,
                    new Poco::Net::TCPServerParams));
                LOG_INFO(log, "Listening for connections with native protocol (tcp) with PROXY: {}", address.toString());
            });
            
            port_name = "tcp_port_secure";
            createServer(listen_host, port_name, listen_try, [&](UInt16 port)