Worker version configuration style flag

https://redmine.teklia.com/issues/10348

The WorkerVersion model should include a new modern_configuration BooleanField, which indicates whether or not each version uses the new configuration system based on the WorkerConfigurationField table. A help_text on the field should explain this. The field defaults to False.

This new field should be editable in the Django admin for worker versions, and should be included in the WorkerVersionSerializer, so that it is available in ListWorkerVersions, RetrieveWorkerVersion, RetrieveRecommendedWorkerVersion and RetrieveFeatureWorkerVersion. It cannot be set through CreateWorkerVersion, UpdateWorkerVersion or PartialUpdateWorkerVersion, as we do not support creating fields through the API at all yet.