Fix specs to account for trilogy

[petergoldstein]

This PR gets the specs green w/trilogy.

Key changes are:

1. Adds trilogy to the sample config
2. Restricts testing of trilogy to ActiveRecord 7.1.0 or later
3. Pulls load_schema out of the database_cleaner version of DatabaseHelper and adds :trilogy to the appropriate when clause. In theory database_cleaner could be updated here instead, but I was confused by the separation and frankly it seemed simpler to pull the whole thing into this gem.

This runs green on my fork.

[etagwerker]

@petergoldstein looks good, thanks!