Ensure all-caps nested consts marked as autoloaded

Previously, an autoloaded constant `HTML::SomeClass` would not be marked
as autoloaded by AS::Dependencies. This is because the
`#loadable_constants_for_path` method uses `String#camelize` on the
inferred file path, which in turn means that, unless otherwise directed,
AS::Dependencies watches for loaded constants in the `Html` namespace.

By passing the original qualified constant name to `#load_or_require`,
this inference step is avoided, and the new constant is picked up in the
correct namespace.