Let `celery-worker` update Step status through DB directly

[Yannick Perrenet]

Describe the problem this improvement solves
Solves technical debt as we previously (pre-notifications) didn't allow the celery-worker to access the DB directly, we had it push the Step status changes (due to Pipeline Runs) to the orchest-api which then updates the DB.

Describe the solution you'd like
Now we can just let the celery-worker interact with the DB directly to update step status.