Use a for loop rather than `partition_map`. We're about to add a third list, so
partition_map won't work.

(partition_map ends up using Vec::push under the hood, so this is pretty much
equivalent.)

... and use it to remove a bit of duplicated code.

The list of boolean arguments is confusing. We may as well just construct the
`DeviceBasedStrategy` directly.

Again, the list of boolean arguments is confusing.

Add (as yet unimplemented) `error_on_verified_user_problem` option

This thing was confusing. What is "legacy" about it?