src: expose MaybeInitializeContext to allow existing contexts

Splits the node.js specific tweak intialization of NewContext into a new
helper MaybeInitializeContext so that embedders with existing contexts
can still use them in a node Environment now that primordials are
initialized and required so early.

src/api/environment.cc

@@ -362,6 +362,13 @@ Local<Context> NewContext(Isolate* isolate,
                           Local<ObjectTemplate> object_template) {
   auto context = Context::New(isolate, nullptr, object_template);
   if (context.IsEmpty()) return context;
+
+  return MaybeInitializeContext(context, object_template);
+}
+
+Local<Context> MaybeInitializeContext(Local<Context> context,
+                                      Local<ObjectTemplate> object_template) {
+  Isolate* isolate = context->GetIsolate();
   HandleScope handle_scope(isolate);
 
   context->SetEmbedderData(ContextEmbedderIndex::kAllowWasmCodeGeneration,

src/node.h

@@ -305,6 +305,12 @@ NODE_EXTERN v8::Local<v8::Context> NewContext(
     v8::Local<v8::ObjectTemplate> object_template =
         v8::Local<v8::ObjectTemplate>());
 
+// Runs Node.js-specific tweaks on an already constructed context
+NODE_EXTERN v8::Local<v8::Context> MaybeInitializeContext(
+    v8::Local<v8::Context> context,
+    v8::Local<v8::ObjectTemplate> object_template =
+        v8::Local<v8::ObjectTemplate>());
+
 // If `platform` is passed, it will be used to register new Worker instances.
 // It can be `nullptr`, in which case creating new Workers inside of
 // Environments that use this `IsolateData` will not work.