dws: move more logic to separate threads #390
Description
Profiling data on LC systems reveals that the coral2_dws script spends most of its time in kubernetes calls. As a step towards fixing #289, it might be a good idea to move more kubernetes logic to separate threads. The logic encapsulated by flux_k8s.workflow.WorkflowInfo.move_to_teardown could be moved to the flux_k8s.cleanup module and that module's coroutines. Also, flux_k8s.storage.init_rabbits could start watching Storage resources in a separate thread.