test: make xvfb start and stop async (angular#64310)

The `xvfb.start()` and `xvfb.stop()` methods are asynchronous but were being called synchronously. This can lead to race conditions where the tests start running before the virtual frame buffer is fully initialized, or the process exits before it's fully stopped.

This commit promisifies the `start` and `stop` methods to ensure they are properly awaited, making the e2e test setup more robust.

PR Close angular#64310

Author: alan-agius4

vscode-ng-language-service/integration/e2e/index.ts

@@ -1,5 +1,6 @@
 import {join} from 'node:path';
 import {homedir, tmpdir} from 'node:os';
+import {promisify} from 'node:util';
 import {runTests} from '@vscode/test-electron';
 
 import {PACKAGE_ROOT, PROJECT_PATH} from '../test_constants';
@@ -17,7 +18,8 @@ async function main() {
   const vsCodeDataDir = await mkdtemp(join(tmpdir(), 'vscode-e2e-'));
 
   try {
-    xvfb.start();
+    await promisify(xvfb.start).call(xvfb);
+
     const exitCode = await runTests({
       // Keep version in sync with vscode engine version in package.json
       version: '1.74.3',
@@ -45,7 +47,7 @@ async function main() {
     console.error('Failed to run tests', err);
     process.exitCode = 1;
   } finally {
-    xvfb.stop();
+    await promisify(xvfb.stop).call(xvfb);
   }
 }