Add kubectl oadp backup resource-status and vm-status commands

[Joeavaikath]

Summary

Add CLI commands that expose per-item backup outcomes using the rollup library from #270.

Parent: #269 (OADP-8697)
Depends on: #270
Design: oadp-operator/docs/design/backup_resource_rollup-design.md (local; pending upstream PR — see parent #269)

Commands

kubectl oadp backup resource-status <backup>

Generic rollup command.

Flags (proposed):

• --group-by=owner:VirtualMachine — group by owning resource kind (also supports owner, label:<key>)
• --namespace — backup namespace (if not inferable)
• -o json|yaml|table — output format (default: failures-first table)
• --group-by-reason — aggregate failures by reason code
• --show-all — include succeeded/skipped rows (default: failures only)

kubectl oadp backup vm-status <backup>

Convenience alias for OADP-8697: resource-status with --group-by=owner:VirtualMachine and VM-oriented column headers.

Default UX

Failures-first table for operability at scale:

$ kubectl oadp backup vm-status oadp-8697-multi-vm-backup
Backup: oadp-8697-multi-vm-backup   Phase: PartiallyFailed
VMs: 5 total   3 succeeded   2 failed   0 skipped

FAILED:
NAME                      NAMESPACE            REASON              DETAIL
vm-broken-baddatasource   oadp-8697-multi-vm   MissingDataSource   ...
vm-broken-orphan-pvc      oadp-8697-multi-vm   MissingPVC          ...

JSON output should be stable for scripting/automation.

Acceptance criteria

• backup resource-status and backup vm-status registered under existing kubectl oadp backup command tree
• Default output shows summary + failed items only; --show-all lists everything
• -o json and -o yaml supported
• Clear error when backup not found or metadata incomplete
• Help text documents --group-by options and relationship to Implement backup resource rollup library (Velero metadata + ownerReference graph) #270 library

Non-goals

• Live backup progress monitoring (see create a generic backup / restore monitor #157)
• Persisting rollup status to a CRD