LSIF: Remove scheduled jobs.

Created by: efritz

This PR moves repeated actions out of the bull queue and into a server-scheduled loop. The tasks are guarded by a postgres advisory lock so that only one server instance is working on the task at a time.

This also removes an endpoint from the API as we no longer need to schedule clean-up tasks. This endpoint was put in place so that we could invoke the update-tips job on demand, but that's since been rolled into the convert job.