LibJS: Move native objects towards two-pass construction

To make sure that everything is set up correctly in objects before we
start adding properties to them, we split cell allocation into 3 steps:

1. Allocate a cell of appropriate size from the Heap
2. Call the C++ constructor on the cell
3. Call initialize() on the constructed object

The job of initialize() is to define all the initial properties.
Doing it in a second pass guarantees that the Object has a valid Shape
and can find its own GlobalObject.

Libraries/LibJS/Runtime/StringObject.cpp

@@ -36,7 +36,7 @@ namespace JS {
 
 StringObject* StringObject::create(GlobalObject& global_object, PrimitiveString& primitive_string)
 {
-    return global_object.heap().allocate<StringObject>(primitive_string, *global_object.string_prototype());
+    return global_object.heap().allocate<StringObject>(global_object, primitive_string, *global_object.string_prototype());
 }
 
 StringObject::StringObject(PrimitiveString& string, Object& prototype)