codeintel: RFC 235: Prepare janitor to be aware of LSIF data in postgres
Created by: efritz
This PR closes https://github.com/sourcegraph/sourcegraph/issues/13887 by removing any pass that deletes upload metadata when it can't correlate data on disk.
All remaining passes may alter the db, but will do so only with data from the db (e.g. missing repos). Others will remove files based on metadata properties, which is still safe. I'd appreciate a quick glance to make sure I'm not missing a situation where upload records can be deleted base on FS state.