To update the right statuses, the controller must collect more information
about why a pod is being evicted. Updating the DeviceTaintRule statuses then is
handled by the same work queue as evicting pods.
Both operations already share the same client instance and thus QPS+server-side
throttling, so they might as well share the same work queue. Deleting pods is
not necessarily more important than informing users or vice-versa, so there is
no strong argument for having different queues.
While at it, switching the unit tests to usage of the same mock work queue as
in staging/src/k8s.io/dynamic-resource-allocation/internal/workqueue. Because
there is no time to add it properly to a staging repo, the implementation gets
copied.
