LSIF: Re-enable dump cleanup
Created by: efritz
https://github.com/sourcegraph/sourcegraph/pull/7486 removed the call to purgeOldDumps
, which makes the cleanup code dead in the eyes of the worker.
This moves the cleanup of dead and outdated dumps to the server, where it is instead run on a schedule. This tasks removes the oldest uploads when the disk is above a configured threshold, and also removes databases that are no longer referenced inside of the postgres db.