Make client more ESM-friendly (#2348)

* Use node: prefix for stdlib imports

* Make code more ESM-friendly

* Add missing mjs file

* Drop mjs file from package.json

test/integration/helpers/msearch.test.js

@@ -19,8 +19,8 @@
 
 'use strict'
 
-const { createReadStream } = require('fs')
-const { join } = require('path')
+const { createReadStream } = require('node:fs')
+const { join } = require('node:path')
 const split = require('split2')
 const { test, beforeEach, afterEach } = require('tap')
 const { waitCluster } = require('../../utils')