Use respawn to speed up tests which need to clean data

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While working on #27372, I'm creating a big test suite that needs to reseed the database between each tests (I can't use transactions to roll back since the implicit transaction in SaveChanges is what's being tested). Our default way for doing this is currently with the database cleaner, which means we reverse-engineer the database, drops all tables and recreate the schema. This takes up far more time than test itself on SQL Server.

We could use respawn instead - that's exactly what it's built to do.