Stale reads on (Partial)UpdateWorkerRun

https://redmine.teklia.com/issues/9053

When updating an existing WorkerRun, it is retrieved from the replica, then a uniqueness check is also done on the replica. The uniqueness check should definitely occur on the default database to avoid a race condition. Users often will update a WorkerRun immediately after creating it, since setting a model version, a configuration, enabling GPU usage or adding dependencies in the frontend requires it, so the retrieval should also be done from the default database.