test: remove hardcoded worker chunk id

This commit changes how we retrieve the worker chunk Id. Prior to this change we hard coded the value, now we get it by reading the file names on disk.

(cherry picked from commit 2925f06)

Author: alan-agius4

tests/legacy-cli/e2e/tests/build/worker.ts

@@ -6,6 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import { readdir } from 'fs/promises';
 import { expectFileToExist, expectFileToMatch, replaceInFile, writeFile } from '../../utils/fs';
 import { ng } from '../../utils/process';
 
@@ -26,7 +27,8 @@ export default async function () {
   await expectFileToMatch('dist/test-project/main.js', 'src_app_app_worker_ts');
 
   await ng('build', '--output-hashing=none');
-  const chunkId = '151';
+
+  const chunkId = await getWorkerChunkId();
   await expectFileToExist(`dist/test-project/${chunkId}.js`);
   await expectFileToMatch('dist/test-project/main.js', chunkId);
 
@@ -53,3 +55,14 @@ export default async function () {
 
   await ng('e2e');
 }
+
+async function getWorkerChunkId(): Promise<string> {
+  const files = await readdir('dist/test-project');
+  const fileName = files.find((f) => /^\d{3}\.js$/.test(f));
+
+  if (!fileName) {
+    throw new Error('Cannot determine worker chunk Id.');
+  }
+
+  return fileName.substring(0, 3);
+}