Add support for public ecr

[fer1592]

Following PR adds support for images hosted in the AWS public registry, aims to solve the following issue. WIP

[davidcollom]

Appreciate the draft PR 👍 - If you're looking for an existing public ECR - we have a deployed version-checker ECR for E2E testing @ public.ecr.aws/c3x5s3k7/public-8456b5e0/alpine which clones alpine:latest

[fer1592]

Quick update about this, using the ecrpublic seems that doesn't work for images on the public.ecr.aws registry. I did a quick test using the http client similarly on how the docker client does, and works well. I'll be updating this PR next week probably (need to clean up all the crap code that I got)

[fer1592]

This should be ready for review. Like mentioned before, I stopped using the public ecr library and just performed http requests for it. I tested it with a couple of images, and seems to be working fine. Eg: for kube-proxy

Let me know what you think!

[davidcollom]

@fer1592 Sorry it's taken so long to get back to this 🙈 - I was curious as to if there was any reasoning around using the OCR Library? or https://github.com/google/go-containerregistry - as a project, we're trying to move away from managing too many client implementations and focusing on the authN/Z portion to the go-containerregistry or native libraries.

This is mainly due to maintenance and testing. We don't have a full E2E testing framework for all of the clients, which can make maintaining them difficult and we rely on the community to report issues and raise PR's to resolve issues.