src,test: add regression test for nested Worker termination

This adds a regression test for terminating a Worker inside which
another Worker is running.

PR-URL: #32623
Refs: #32531
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>

Author: addaleax

src/env.cc

@@ -1014,6 +1014,8 @@ void Environment::Exit(int exit_code) {
 }
 
 void Environment::stop_sub_worker_contexts() {
+  DCHECK_EQ(Isolate::GetCurrent(), isolate());
+
   while (!sub_worker_contexts_.empty()) {
     Worker* w = *sub_worker_contexts_.begin();
     remove_sub_worker_context(w);

test/parallel/test-worker-terminate-nested.js

@@ -0,0 +1,15 @@
+'use strict';
+const common = require('../common');
+const { Worker } = require('worker_threads');
+
+// Check that a Worker that's running another Worker can be terminated.
+
+const worker = new Worker(`
+const { Worker, parentPort } = require('worker_threads');
+const worker = new Worker('setInterval(() => {}, 10);', { eval: true });
+worker.on('online', () => {
+  parentPort.postMessage({});
+});
+`, { eval: true });
+
+worker.on('message', common.mustCall(() => worker.terminate()));