module: make synthetic module evaluation steps return a Promise to su…

…pport top level await

Top level await expects that all module script evaluation returns a
Promise. As such, update
ModuleWrap::SyntheticModuleEvaluationStepsCallback to return a
resolved Promise now that V8 has enabled top-level await by default.

Unfortunately I don't have a spec reference that I can point to here
because the Built-in modules proposal isn't yet updated for
top level await.

The corresponding change for Blink is
https://chromium-review.googlesource.com/c/chromium/src/+/2568823.

This will allow a workaround for Node in this V8 bugfix to be removed:
https://chromium-review.googlesource.com/c/v8/v8/+/2673794.

Fixes: #37299

PR-URL: #37300
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

src/module_wrap.cc

@@ -665,7 +665,14 @@ MaybeLocal<Value> ModuleWrap::SyntheticModuleEvaluationStepsCallback(
     try_catch.ReThrow();
     return MaybeLocal<Value>();
   }
-  return Undefined(isolate);
+
+  Local<Promise::Resolver> resolver;
+  if (!Promise::Resolver::New(context).ToLocal(&resolver)) {
+    return MaybeLocal<Value>();
+  }
+
+  resolver->Resolve(context, Undefined(isolate)).ToChecked();
+  return resolver->GetPromise();
 }
 
 void ModuleWrap::SetSyntheticExport(const FunctionCallbackInfo<Value>& args) {