Extract auto-login code to fluxcd/pkg

[stefanprodan]

As described in the RFC Flux OCI support for Kubernetes manifests, source-controller will have to use the same flags and authentication logic for Azure, AWS and Google Cloud as implemented in this controller.

We need to extract the auto-login code and the flags: --aws-autologin-for-ecr, --azure-autologin-for-acr, --gcp-autologin-for-gcr to a dedicated package in fluxcd/pkg/oci/auth so that we can share the code between image-reflector-controller and source-controller.

[withnale]

I was searching for this issue on the source-controller but have found it here. Is there an eta on this?

The workload-identity logic works well in image-reflector, but I assume to get source-controller (and HelmRepository) able to use oci: then this card will need to be actioned and this logic be available in both apps?