Stopgap: Import 5GB+ repo workaround

Based on the summary by @lyle in this comment and the ensuing discussion, I'd like to break off into an issue to discuss how to continue to support a workaround solution to the problem of importing large 5GB+ repos to gitlab.com while the manage:import team builds a true productized solution.

I understand that there are staffing concerns on both product and infrastructure teams that caused us to deprecate this workaround process in the first place. Hoping to have a discussion about creative staffing solutions to continue to support this process while we wait for the productized solution to become available.

@hdelalic @marin @michael_lutz @dsakamoto @adawar @cynthia @juliebyrne @rknight2