Report Tenant Tiers Usage in Status

[dvaldivia]

This PR adds the report of the tiers usage from MinIO to the .status.usage.tiers field. This is to more accurately report the usage by the tenant.

Example:

status:
  usage:
    capacity: 7463196033024
    rawCapacity: 1099511627776
    rawUsage: 3107523919872
    tiers:
    - Name: STANDARD
      Type: internal
      totalSize: 58249152
    - Name: MINIO_TIER_1
      Type: s3
      totalSize: 149606428
    usage: 149606428

Signed-off-by: Daniel Valdivia 18384552+dvaldivia@users.noreply.github.com