List resources in the test namespace when deleting it times out

[porridge]

What would you like to be added:

When kuttl fails to delete a namespace, attempt to list at least types and names of resources that remain there. Perhaps the namespace too, to see any finalizer fields.

Why is this needed:

When running in an automated CI system, in which the whole cluster is wiped afterwards, it is rather difficult to find out why namespace deletion failed. One just sees:

    logger.go:42: 11:14:53 | upgrade | Deleting namespace: kuttl-test-trusty-rabbit
    case.go:114: timed out waiting for the condition

It would be possible but a bit hacky to list contents of leftover kuttl namespaces from outside it afterwards. Much nicer if this capability was built into kuttl.