test: fix flaky test-worker-debug

Address a race condition in the test; the Worker’s exit events
may have been not recorded because the Worker exited before
the listeners were attached.

Fix the by attaching the event listeners before telling the Worker
to exit.

Fixes: nodejs#28299
Fixes: nodejs#28106

Author: addaleax

test/parallel/parallel.status

@@ -21,8 +21,6 @@ test-worker-memory: PASS,FLAKY
 test-http2-client-upload: PASS,FLAKY
 # https://github.com/nodejs/node/issues/20750
 test-http2-client-upload-reject: PASS,FLAKY
-# https://github.com/nodejs/node/issues/28106
-test-worker-debug: PASS,FLAKY
 
 [$system==linux]
 

test/parallel/test-worker-debug.js

@@ -240,11 +240,17 @@ async function testWaitForDisconnectInWorker(session, post) {
   });
   await workerSession1.post('Runtime.runIfWaitingForDebugger');
 
+  // Create the promises before sending the exit message to the Worker in order
+  // to avoid race conditions.
+  const disconnectPromise =
+    waitForEvent(workerSession1, 'NodeRuntime.waitingForDisconnect');
+  const executionContextDestroyedPromise =
+    waitForEvent(workerSession2, 'Runtime.executionContextDestroyed');
   worker.postMessage('resume');
 
-  await waitForEvent(workerSession1, 'NodeRuntime.waitingForDisconnect');
+  await disconnectPromise;
   post('NodeWorker.detach', { sessionId: sessionId1 });
-  await waitForEvent(workerSession2, 'Runtime.executionContextDestroyed');
+  await executionContextDestroyedPromise;
 
   await exitPromise;