Worker: lock jobs by executors

[infherny]

The goal of this MR is to add the ability to lock jobs by executors.

[isra17]

This won't really work. You select all jobs from the database then filter them. But the get_unassigned_queues returns up to N jobs, so it might only select the wrong job and not return any job using your executor.

We probably need to do the other way around: read the potential jobs from the static_definitions with our executor selector, then get_unassigned_queues that match one of these job.

It's ugly and inneficient, but that's the quickest and most reliable hack for now.

[infherny]

What about removing this limit when we specify an executor?

if len(assigned_items) < max_assigned_items:
        assigned_items.extend(
            queues_store.get_unassigned_queues(
                session=session,
                assigned_before=assignation_expiration_cutoff,
                limit=max_assigned_items - len(assigned_items) if not lock_input.executiors,
                selector=lock_input.selector,
            )
        )

[infherny]

I implemented the limit suggestion