use node: prefix for requires

mostly because code is being autogenerated by all the AI stuff using
this prefix. it's also used in the stack trace.

src/dig.js

@@ -4,9 +4,9 @@ exports = module.exports = {
     resolve,
 };
 
-const assert = require('assert'),
+const assert = require('node:assert'),
     constants = require('./constants.js'),
-    dns = require('dns');
+    dns = require('node:dns');
 
 // a note on TXT records. It doesn't have quotes ("") at the DNS level. Those quotes
 // are added for DNS server software to enclose spaces. Such quotes may also be returned