Support --artifact-platform in oras attach?

[Wwwsylvia]

In #1066, we discussed adding platform information into the artifact manifest. Now we have implemented the --artifact-platform flag for oras push, we should also consider if it's helpful to add the same functionality to oras attach.

It would be something like:

oras attach localhost:5000/oras:v1.0.1 --artifact-type "application/vnd.sbom" --artifact-platform linux/amd64 oras--1.0.1.arm64_monterey.bottle.tar.gz

[FeynmanZhou]

It may require a valid scenario to justify why platform information is necessary for a referrer artifact. Suggest keeping this issue open for discussion and feedback gathering from the community.