feat: Re-query the DNS during reconnection

[franktz]

中文：
在 WebSocket 长连接场景中此功能尤为重要。
启用 reconn_setting_t 重连接功能后，客户端在重新建立连接时会再次进行 DNS 查询，以获取最新的 IP 地址，从而避免因 DNS 切换导致无法连接服务的问题。该机制通常用于同一域名下主从 IP 切换的重连场景：先完成 DNS 切换，再停止旧服务，使连接在重连时能够成功接入新的服务节点。

English:
This mechanism is especially critical for WebSocket long-lived connections and is strongly recommended to be enabled.
When the reconn_setting_t reconnection feature is enabled, the client performs a DNS lookup again during reconnection to obtain the latest IP address. This prevents connection failures caused by DNS changes. This mechanism is commonly used in reconnection scenarios involving primary/secondary IP switching under the same domain name: the DNS is switched first, then the old service is stopped, allowing the reconnection to successfully connect to the new service node.

[ithewei]

I suggest to add if (reconn_setting && reconn_setting->cur_retry_cnt > 1) to use the old address on the first reconnection to speed up the reconnection process.

[ithewei]

int connfd = -1;
if (reconn_setting && reconn_setting->cur_retry_cnt > 1) {
    connfd = createsocket(remote_port, remote_host.c_str());
} else {
    connfd = createsocket(&remote_addr.sa);
}