hns CLI: describe command should also describe allowCascadingDeletion property

[manjinder-mckc]

Current Output:

$ kubectl hns describe boss                             
Hierarchy configuration for namespace boss
  Parent:  bigboss
  Children:
  - workers (subnamespace)
  No conditions

Expected Output:

$ kubectl hns describe boss                             
Hierarchy configuration for namespace boss
  Parent:  bigboss
  Children:
  - workers (subnamespace)
  AllowCascadingDeletion: true
  No conditions

Proposing Changes here: https://github.com/kubernetes-sigs/hierarchical-namespaces/blob/564b4a968ca2091f27cf0eb51d0cd99190e57db5/internal/kubectl/describe.go#L33-L83

Would be willing to raise a PR, if you guys agree that this makes sense.