[promises] port NewPromiseCapability to TF

src/promise-utils.h

Index: src/promise-utils.h
diff --git a/src/promise-utils.h b/src/promise-utils.h
index 740cd01836ac32608b00bfe153473a05cf77847d..ff7f508fee6971714bff1f935dfde5a6822f3b5e 100644
--- a/src/promise-utils.h
+++ b/src/promise-utils.h
@@ -40,6 +40,16 @@ class PromiseUtils : public AllStatic {
                                        Handle<JSFunction>* resolve,
                                        Handle<JSFunction>* reject);
 };
+
+class GetPromiseCapabilityExecutor : public AllStatic {
+ public:
+  enum FunctionContextSlot {
+    kCapabilitySlot = Context::MIN_CONTEXT_SLOTS,
+
+    kContextLength,
+  };
+};
+
 }  // namespace internal
 }  // namespace v8