[ECR] [console multi-arch support]: Support viewing multi-architecture images in the ECR Console UI correctly

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**Tell us about your request**

Currently, if I were to push a multiple architecture build to ECR, it would show up in the console as multiple images. Let's say I pushed an image that was built for `linux/amd64` and `linux/arm64` and tagged it as "latest", three different images would show up in ECR

1. the digest for linux/amd64 showing as ``
2. the digest for linux/arm64 showing as ``
3. The digest that points to the manifest that points to the images in 1/2 showing as `latest`

This is the correct behavior and pulling and interacting with these images via the `docker` CLI works exactly as expected. However, looking at the ECR UI is extremely confusing because it shows as 3 images. Displaying it as one image with multiple architecture would be less confusing and would bring ECR to feature parity with [the official docker repository](https://hub.docker.com/_/alpine?tab=tags).

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

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
It's extremely confusing and looks like we accidentally published 3 images (or worse, pushed images but didn't tag them). It shouldn't take knowledge of Docker's implementation of mult-arch images to understand the ECR UI.

Note that this is more important than it used to be because of the Apple Silicon MBPs that were recently released - we're transitioning to publishing more images with multiple architectures and I imagine others are as well.

**Are you currently working around this issue?**
It's mostly a messaging problem - we have to explain this behavioral quirk as an issue with the UI. It'd be nice if we didn't have to.

Start by reproducing the ECR Console behavior with a Docker image manifest containing linux/amd64 and linux/arm64 images, then compare the console listing with Docker's repository presentation. Confirm how the tagged manifest and architecture-specific digests are currently displayed. Done means the console presents the multi-architecture image as one understandable image while retaining access to its architectures.

Written by the indexing model from the issue text.