LibJS: Remove Object::value_of()

Being really close to Object.prototype.valueOf() name wise makes this
unnecessarily confusing - while it sometimes serves as the
implementation of a valueOf() function, it's an abstraction which the
spec doesn't have.
Use the appropriate getters to retrieve specific internal slots instead,
most commonly [[FooData]] from the primitive wrapper objects.
For the Object class specifically, use the Value(Object*) ctor instead.

Userland/Utilities/js.cpp

@@ -760,7 +760,7 @@ static void print_primitive_wrapper_object(FlyString const& name, JS::Object con
     // BooleanObject, NumberObject, StringObject
     print_type(name);
     js_out(" ");
-    print_value(object.value_of(), seen_objects);
+    print_value(&object, seen_objects);
 }
 
 static void print_value(JS::Value value, HashTable<JS::Object*>& seen_objects)