Extend RetrieveWorkerRun

To configure() a worker, we need more information from RetrieveWorkerRun (to avoid a lot of followup queries AND to support the frontend display needs in next release):

• the full worker version payload along with its configuration
• the worker configuration
• the process details

We could simply extend the serializer with these fields: worker_version, process and configuration, leaving worker_version_id, dataimport_id and configuration_id as is.

I only see 2 usages currently of these IDs:

• bootstrap of base-worker (in configure())
• frontend usage to manage worker runs (i'm not sure).

Or we could straight blast them, but that would kill all old workers (which is not great...)