Clarify the brief of container.image.id

[ChrsMark]

The container.image.id attribute includes in it's a brief a note about K8s which is not really accurate:

K8s defines a link to the container registry repository with digest "imageID": "registry.azurecr.io/namespace/service/dockerfile@sha256:bdeabd40c3a8a492eaf9e8e44d0ebbb84bac7ee25ac0cf8a7159d25f62555625".

This was explained in a respective Collector's implementation attempt at open-telemetry/opentelemetry-collector-contrib#32314 (comment).

This brief should most probably reflect the following from open-telemetry/opentelemetry-collector-contrib#32314 (comment):

I think one way to proceed is to also use the github.com/distribution/reference package to attempt to parse the output of .imageID from the k8s API response. If it is a canonical reference, then populate the semantic attribute container.image.repo_digests with those values (of which it seems there will only be one from the existing CRI implementations (?)). If it is not, then populate container.image.id.

refs:

• Enable retrieving container.image.repo_digests attribute in k8sattributes processor opentelemetry-collector-contrib#34029
• [processor/k8sattributes] Add container.image.repo_digests opentelemetry-collector-contrib#34031

/cc @lmolkova @evantorrie