Massive multi-create testing, with two regression fixes:

Massive multi-create testing, with two regression fixes:
- An uninserted row must be passed to find_or_create_related with all uninserted objects on which it depends. Since currently we store those in {_inflated_column} as opposed to {_relationship_data} as we should, a simple ->get_inflated_columns will suffice
- We must find_or_create related rows, as find_or_new might queue multiple identical objects for insertions, which will subsequently violate existing unique constraints