Add nightly integration tests for modifying org storage

[tw4l]

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Follow-up to #2093

Related to #578

The backend tests for org storage cover adding and removing a custom storage, as well as setting the primary and replica storage locations for an organization that hasn't yet crawled anything.

When primary and/or replica storage locations are changed in an organization that already has stored crawl, upload, and/or browser profile files, file migrations take place via backend jobs. We should cover this end-to-end process via integration tests, verifying that the migration completes as expected, all files have been successfully transferred, and downloading/replaying files works as expected.