Support seamless schema migration on S3 from V11 to V12

The Loki-Operator should ensure seamless upgrades of the lokistack schema configuration when using S3 as object storage from V11 to V12.

Acceptance Criteria

• The Loki-Operator ensures an one-time persistent migration from V11 to V12.
• New Lokistack installation start always with V11 per default.

Developer Notes

• Gradual index schema migrations can be done by using date-range-based schema configuration:

  schema_config: 
    configs: 
      - from: "2020-10-01"
        index: 
          period: 24h
          prefix: index_
        object_store: s3
        schema: v11
        store: boltdb-shipper schema_config: 
      - from: "2022-05-01"
        index: 
          period: 24h
          prefix: index_
        object_store: s3
        schema: v12
        store: boltdb-shipper
   

  e.g. https://grafana.com/docs/loki/latest/storage/#schema-configs

• Schema Migration require to define a from date in the future. From an operator perspective we cannot hardcode anything here, because we don't know when users will upgrade to cluster. This mean we may need an active eval-loop from the loki operator side. Alternatively we need to open the API for users to opt-in via the ObjectStorageSpec.