[ECR] [pull-through cache]: Add registry.access.redhat.com source

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**Tell us about your request**
Enable ECR pull-through-cache to pull `registry.access.redhat.com/ubi9-minimal:9.4` and similar images.

**Which service(s) is this request for?**
ECR

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**

Red Hat Enterprise Linux 9 Universal Base Image is a free-to-use, free-to-distribute container base image. When building a container image that utilizes this, inside AWS, we would like to pull only images that come through the ECS pull-through cache and that are scanned by AWS image scanning tools. As such, we would like to pull `registry.access.redhat.com/ubi9-minimal:9.4` and similar images from `registry.access.redhat.com` through the ECR pull-through cache mechanism. This is not currently a possible.

**Are you currently working around this issue?**
We are pulling directly from `registry.access.redhat.com` and not using ECR as our image source. Alternately, we may develop a workflow to pull from registry.access.redhat.com and then push to ECR, mimicking ECR pull-through-cache for this source.

Start by reviewing the ECR pull-through-cache request for registry.access.redhat.com and the example ubi9-minimal:9.4 image. Confirm the expected behavior for pulling similar images through ECR and AWS image scanning; the issue does not name repository files, tests, or an implementation entry point.

Written by the indexing model from the issue text.