Remove database and collection cleanup from $config.teardown functions

As mentioned in this comment of SERVER-34548, having FSM workloads drop their (unique) database or collection in the $config.teardown() function undermines our data consistency checks as the contents will be deleted before the resmoke.py hooks run. We should leave it to the CleanupConcurrencyWorkloads hook from SERVER-30204 to drop all the databases and collections after the data consistency checks run.