Support showing more information of tags in formatted output

[FeynmanZhou]

What is the version of your ORAS CLI

v1.2.0

What would you like to be added?

When listing the tags in an OCI image layout or an repo within OCI registry. The digest and platform information can be listed alongside the tags in the output.

$ oras repo tags --oci-layout layout-dir --format json

{
  "reference": "localhost:5000/oras@sha256:7414904f07f515f48fe4afeaf876e3151039a81e7177b9c66e9e7ed6dd186111",
  "tags": [
    {
      "tag": "v1"
      "digest": "sha256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
      "mediaType": "application/vnd.oci.image.index.v1+json",
      "size": 820
    },
     {
      "tag": "v1-linux-amd64"
      "digest": "sha256:yyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyyy",
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "size": 200
    },
    {
      "tag": "v1-linux-arm64"
      "digest": "sha256:zzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz",
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "size": 200
    },
  ]
}

Why is this needed for ORAS?

• With the media type of each tag showing in the formatted output, users should be able to differentiate from an image index and image manifest in a repo
• Easier to users to list all available tags with their descriptor in a repo, so that users can compose an image index by selecting from a few arch-specific tags
• For scripting and automation scenario

Are you willing to submit PRs to contribute to this feature?

• Yes, I am willing to implement it.

[shizhMSFT]

Besides the output formatting minor issues, there is a perf concern: if a repo has hundreds of tags, this command will appear to hang without any response.