Add support for EKS Pod Identity

[ripa1993]

Is your feature request related to a problem? Please describe.

AWS has introduced EKS Pod Identity as a new way for authenticating Kubernetes Pods against AWS APIs.

Describe the solution you'd like

This requires upgrading the Go AWS SDK v2 to at least 1.23.0, currently 1.16.0 is being used by dependency thanos-io/objstore

Describe alternatives you've considered

Using IRSA (iam roles for service accounts) for Mimir, but I would prefer to stick with EKS Pod Identity for uniformity with other tools running in Kubernetes

Additional context

Add any other context or screenshots about the feature request here.

Linked issue: thanos-io/objstore#131