[test] Give more time to GC in test-shadow-realm-gc

Partial cherry-pick of nodejs#50735

test/common/gc.js

@@ -1,5 +1,7 @@
 'use strict';
 
+const wait = require('timers/promises').setTimeout;
+
 // TODO(joyeecheung): merge ongc.js and gcUntil from common/index.js
 // into this.
 
@@ -65,6 +67,15 @@ async function checkIfCollectable(
   createObject();
 }
 
+// Repeat an operation and give GC some breathing room at every iteration.
+async function runAndBreathe(fn, repeat, waitTime = 20) {
+  for (let i = 0; i < repeat; i++) {
+    await fn();
+    await wait(waitTime);
+  }
+}
+
 module.exports = {
   checkIfCollectable,
+  runAndBreathe,
 };

test/parallel/test-shadow-realm-gc.js

@@ -6,14 +6,16 @@
  */
 
 const common = require('../common');
+const { runAndBreathe } = require('../common/gc');
 const assert = require('assert');
 const { isMainThread, Worker } = require('worker_threads');
 
-for (let i = 0; i < 100; i++) {
+runAndBreathe(() => {
   const realm = new ShadowRealm();
   realm.evaluate('new TextEncoder(); 1;');
-}
+}, 100).then(common.mustCall());
 
+//Test it in worker too.
 if (isMainThread) {
   const worker = new Worker(__filename);
   worker.on('exit', common.mustCall((code) => {