[promises] Clean up promise utils and remove dead code

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index 0b7aaae817e89fb1074bc9898df053eef98b6d1a..c2aa069810e30b1d878c0d1fbd388ec167512bb7 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -69,12 +69,6 @@ class V8_EXPORT_PRIVATE Factory final {
   // Create a new boxed value.
   Handle<Box> NewBox(Handle<Object> value);
 
-  // Create a new PromiseReactionJobInfo struct.
-  Handle<PromiseReactionJobInfo> NewPromiseReactionJobInfo(
-      Handle<Object> value, Handle<Object> tasks,
-      Handle<Object> deferred_promise, Handle<Object> deferred_on_resolve,
-      Handle<Object> deferred_on_reject, Handle<Context> context);
-
   // Create a new PrototypeInfo struct.
   Handle<PrototypeInfo> NewPrototypeInfo();
 
@@ -320,8 +314,6 @@ class V8_EXPORT_PRIVATE Factory final {
   Handle<Context> NewBlockContext(Handle<JSFunction> function,
                                   Handle<Context> previous,
                                   Handle<ScopeInfo> scope_info);
-  // Create a promise context.
-  Handle<Context> NewPromiseResolvingFunctionContext(int length);
 
   // Allocate a new struct.  The struct is pretenured (allocated directly in
   // the old generation).