src: dispose of V8 platform in process.exit()

Calling `process.exit()` calls the C `exit()` function, which in turn
calls the destructors of static C++ objects. This can lead to race
conditions with other concurrently executing threads; disposing of all
Worker threads and then the V8 platform instance helps with this
(although it might not be a full solution for all problems of
this kind).

Refs: nodejs#24403
Refs: nodejs#25007

src/env.cc

@@ -857,10 +857,13 @@ void Environment::AsyncHooks::grow_async_ids_stack() {
 uv_key_t Environment::thread_local_env = {};
 
 void Environment::Exit(int exit_code) {
-  if (is_main_thread())
+  if (is_main_thread()) {
+    stop_sub_worker_contexts();
+    DisposePlatform();
     exit(exit_code);
-  else
+  } else {
     worker_context_->Exit(exit_code);
+  }
 }
 
 void Environment::stop_sub_worker_contexts() {

src/node.cc

@@ -340,6 +340,10 @@ tracing::AgentWriterHandle* GetTracingAgentWriter() {
   return v8_platform.GetTracingAgentWriter();
 }
 
+void DisposePlatform() {
+  v8_platform.Dispose();
+}
+
 #ifdef __POSIX__
 static const unsigned kMaxSignal = 32;
 #endif

src/node_internals.h

@@ -357,6 +357,7 @@ int ThreadPoolWork::CancelWork() {
 }
 
 tracing::AgentWriterHandle* GetTracingAgentWriter();
+void DisposePlatform();
 
 static inline const char* errno_string(int errorno) {
 #define ERRNO_CASE(e)  case e: return #e;