New lookups were added to `auto_lookups`, which means that they were processed after the prefetches for the current level.

This meant that nested prefetches couldn't be referred to by a later prefetch:

```python
house_queryset = House.objects.prefetch_related('rooms', to_attr='room_list')
Person.objects.prefetch_related(
    Prefetch('houses', queryset=house_queryset, to_attr='houses_lst'),
    Prefetch('houses_lst__rooms_lst__something)
)
```