test: generalize webpack direct E2E chunk size testing

Updates to `webpack` or any of the used Webpack plugins can cause output
chunk identifiers to change. The `packages/webpack/test-app` E2E test
previously hard coded these file name identifiers into the test which
can cause unexpected test failures when packages are updated. To remedy
this situation, the output file contents are now checked to discover any
files.

(cherry picked from commit 5759cde)

tests/legacy-cli/e2e/tests/packages/webpack/test-app.ts

@@ -1,7 +1,9 @@
-import { normalize } from 'path';
+import { join, normalize } from 'path';
 import { createProjectFromAsset } from '../../../utils/assets';
 import { expectFileSizeToBeUnder, expectFileToMatch, replaceInFile } from '../../../utils/fs';
 import { execWithEnv } from '../../../utils/process';
+import { readdir } from 'node:fs/promises';
+import assert from 'node:assert';
 
 export default async function () {
   const webpackCLIBin = normalize('node_modules/.bin/webpack-cli');
@@ -14,9 +16,17 @@ export default async function () {
 
   // Note: these sizes are without Build Optimizer or any advanced optimizations in the CLI.
   await expectFileSizeToBeUnder('dist/app.main.js', 650 * 1024);
-  await expectFileSizeToBeUnder('dist/604.app.main.js', 1024);
-  await expectFileSizeToBeUnder('dist/988.app.main.js', 1024);
-  await expectFileSizeToBeUnder('dist/896.app.main.js', 1024);
+  const outputFiles = await readdir('dist', { withFileTypes: true });
+  let fileCount = 0;
+  for (const outputFile of outputFiles) {
+    if (outputFile.isFile() && outputFile.name.endsWith('.app.main.js')) {
+      ++fileCount;
+      await expectFileSizeToBeUnder(join(outputFile.path, outputFile.name), 1024);
+    }
+  }
+  if (fileCount !== 3) {
+    assert.fail('Expected three additional Webpack output chunk files.');
+  }
 
   // test resource urls without ./
   await replaceInFile('app/app.component.ts', './app.component.html', 'app.component.html');