Is your feature request related to a problem? Please describe.
In our Kubernetes environment, we don't put our AWS creds on our pods, but rather, we use KIAM and proxy all our AWS requests through it where it then attaches the correct creds based on the IAM role we annotate the pods with. I would think a good feature would be to specify an environment variable (something like USE_KUBE_IAM_ROLE) that when set to true bypasses the AWS cred provider initialization in s3.go

Describe the solution you'd like

1. specify an environment variable (something like USE_KUBE_IAM_ROLE)
2. When the above env variable is set to true, bypass the AWS cred provider initialization in s3.go and go straight to creating the AWS Session
3. Add a field in the helm template to specify a pod annotation for the IAM Role and the new environment variable.

Additional context
I have a fork with this change but I was having issues with github creds locally, I can post it when I have resolved these.