As of now, we have two tests for magic restore that test non-PIT and PIT cases for replica sets. There's a lot of duplicate code and assertions in both tests. We'll want to add more targeted tests, and to make that easier, we should modularize the magic restore jstests.

We should move common functionality for magic restore into backup_utils.js as much as possible. The goal is to make the tests easy to write by focusing on the particular target of the test.

If applicable, we can split the behavior of the existing two tests into multiple tests to make them easier to work with.