deposit: Separate loader and checker services
To improve the feedback loop for deposit's clients when the main archive's services are down. Typically, as the checker does not touch the main archive's storage, it can stay up and do its checks.
Related T1918
Test Plan
bin/octocatalog on a worker on azure. Expectedly wants to:
- add the checker_deposit service
- decrease concurrency of loader service from 2 to 1 (it was at 2 when both services where merged together, so i decreased it)
Migrated from D1740 (view on Phabricator)