feat(enterprise): add tiered-storage administration commands

[xe-nvdk]

Context

Arc Enterprise exposes tiered-storage status, file inspection, migration, scanning, statistics, and per-database policies. arcli currently has no /api/v1/tiering/* coverage.

Scope

Add a arcli tiering command tree covering:

• status
• files, including the server's available database/tier filters and pagination
• migrate
• stats
• scan
• policy list, show, set, delete, and effective

Map directly to /api/v1/tiering/{status,files,migrate,stats,scan} and /api/v1/tiering/policies/*.

Acceptance criteria

• Every tiering endpoint above is represented
• File listings are bounded and pagination is scriptable
• Policy input validates database names and non-negative age values before making a request
• List commands support table, JSON, and CSV; object commands support table and JSON
• Policy deletion prompts and supports --yes
• Enterprise-license and admin-permission failures are reported clearly
• Typed client and command tests cover server response shapes and error paths
• README/help and release notes document the commands