Remove storage chunks clients

[09jvilla]

No description provided.

[09jvilla]

From @pstibrany

I believe 527 is about removing pkg/chunk/aws, pkg/chunk/gcp, pkg/chunk/cassandra, basically everything that implements ObjectClient and IndexClient interfaces.

It's not used outside of chunks code.

ideally entire pkg/chunk should be gone, but there may be bits that are still needed

see https://raintank-corp.slack.com/archives/C029912SXT8/p1641315878026300?thread_ts=1641311201.022900&cid=C029912SXT8

[simonswine]

The majority of the packages underneath github.com/grafana/mimir/pkg/chunk should be removed as part of this work.

This make sense to touch after #525

As ticket #5 mentions, parts of the purger are still relevant in particular:

• pkg/chunk/purger/tenant_deletion_api.go

[pracucci]

I addressed this in #755.