Consider adding OCI Image Annotations to .NET images

[lbussell]

See the list of pre-defined OCI image annotations here:

https://github.com/opencontainers/image-spec/blob/main/annotations.md#pre-defined-annotation-keys

Several of these annotations overlap with our image-info.json spec. Of note are:

• org.opencontainers.image.created
• org.opencontainers.image.source
• org.opencontainers.image.base.digest
• org.opencontainers.image.base.name

(The base image annotations were added to the spec in 2021)

We have already computed lots of this information when we build our images. We should consider adding these annotation to image manifests in addition to (or instead of) tracking it ourselves in image-info.json files.

[lbussell]

[Triage] This has potential to simplify our image info file if we can use this to check for base image updates. However, it may be less practical to use if we would need to submit a separate request to MCR for each image's manifest instead of sending one request to grab our image info file for all of the current base image digests.

[lbussell]

This seems to have limited ROI for us at the moment. If there are any users who would benefit from the addition of these OCI image annotations, we would like to hear about your scenario.

I'll leave this issue open to solicit discussion for a while.