[IAM Credentials Migration] [Code build & CR package] [eks-anywhere-packages] Use session token in building AWS config if provided

[rajeshvenkata]

In eks-anywhere-packages, add changes in below code to use session token

https://github.com/aws/eks-anywhere-packages/blob/11a71d073fd463371fae274ff8883687a9be91c9/credentialproviderpackage/pkg/awscred/awscred.go#L14https://github.com/aws/eks-anywhere-packages/blob/11a71d073fd463371fae274ff8883687a9be91c9/pkg/registry/ecr_cred_injector.go#L29