Manage digest-only images same way as images with tags.

**What is the problem you're trying to solve**
I would like to have clearer path for managing __not-tagged__ images in ACR.
Currently, using Docker Hardened Images (DHI), especially with DHI Helm charts, is problematic (confusing) in ACR, due to the fact, that DHI use image digest instead of tag. Therefore, when the AKS deployment pulls image using its digest, the image is not visible at the image list in Azure Portal.
As I understand, the image is not visible because it does not have the tag. But it of course has digest.

**Describe the solution you'd like**
Digest should be managed in the same way as tags with images.

**Additional context**
This issue is created based on suggestion from here: https://github.com/Azure/acr/issues/862#issuecomment-4453005169

Just let me also paste the questions that I've created in the above Issue:
_In my ACR there are only images with tag (when checking via Portal).
When I do pull with sha256 the image is not visible in ACR.
How can I check if it is really there?
And if it is there, how can I manage it? Delete it?
Should I use "az acr manifest delete" for that?
Running "az acr manifest list" I gives me also the images pulled only by sha256.
Does it mean, that if the manifest with previously pulled sha256 is in ACR, then that image is stored/cached in ACR? So the manifest is not the "metadata" (as I understand it now) but it points to actual image?_

Start with the Azure Portal image list and the `az acr manifest list` and `az acr manifest delete` entry points described in the issue. Compare how digest-only manifests from AKS pulls are represented and managed versus tagged images. Done means digest-only images are visible and can be managed consistently with tagged images.

Written by the indexing model from the issue text.