fix(workers): Make worker.terminate() not immediately kill the isolate (#12831)

Due to a bug in V8, terminating an isolate while a module with top-level
await is being evaluated would crash the process. This change makes it
so calling `worker.terminate()` will signal the worker to terminate at
the next iteration of the event loop, and it schedules a proper
termination of the worker's isolate after 2 seconds.

cli/tests/integration/worker_tests.rs

@@ -99,3 +99,8 @@ itest!(worker_permissions_blob_local {
   http_server: true,
   exit_code: 1,
 });
+
+itest!(worker_terminate_tla_crash {
+  args: "run --quiet --reload workers/terminate_tla_crash.js",
+  output: "workers/terminate_tla_crash.js.out",
+});