新增于: v10.6.0
使用域名系统协议解析 hostname 的指针记录（PTR 记录）。当成功时，Promise 使用包含响应记录的字符串数组进行解决。
¥Uses the DNS protocol to resolve pointer records (PTR records) for the
hostname. On success, the Promise is resolved with an array of strings
containing the reply records.