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/apptaskmanager.js

@@ -5,12 +5,12 @@ exports = module.exports = {
     scheduleTask
 };
 
-const assert = require('assert'),
+const assert = require('node:assert'),
     BoxError = require('./boxerror.js'),
     debug = require('debug')('box:apptaskmanager'),
-    fs = require('fs'),
+    fs = require('node:fs'),
     locks = require('./locks.js'),
-    path = require('path'),
+    path = require('node:path'),
     paths = require('./paths.js'),
     safe = require('safetydance'),
     scheduler = require('./scheduler.js'),