src: run RunBeforeExitCallbacks as part of EmitBeforeExit

This is part of a series of changes to make embedding easier, by
requiring fewer internal methods to build a fully functioning
Node.js instance.

This also aligns the worker_threads code with the main thread code.

src/api/hooks.cc

@@ -30,6 +30,8 @@ void AtExit(Environment* env, void (*cb)(void* arg), void* arg) {
 }
 
 void EmitBeforeExit(Environment* env) {
+  env->RunBeforeExitCallbacks();
+
   HandleScope handle_scope(env->isolate());
   Context::Scope context_scope(env->context());
   Local<Value> exit_code = env->process_object()

src/node_main_instance.cc

@@ -136,8 +136,6 @@ int NodeMainInstance::Run() {
         more = uv_loop_alive(env->event_loop());
         if (more && !env->is_stopping()) continue;
 
-        env->RunBeforeExitCallbacks();
-
         if (!uv_loop_alive(env->event_loop())) {
           EmitBeforeExit(env.get());
         }