Support automatic conversion of Docker V2 manifests to the OCI manifest format

[adamfowleruk]

Is your feature request related to a problem? Please describe.

Some container registries (E.g. zot) only support OCI format manifests. It would be desirable for zarf to have an option in zarf package create such as --oci-manifests-only that used skopeo to fetch the container images and automatically convert to the OCI format.

This is related to the tar.gz image support I've just commented on in #2181

Describe the solution you'd like

• Given a container image in the docker v2 manifest format
• When I run zarf package create . --oci-manifests-only
• Then conversion to OCI manifest format occurs during package creation

Describe alternatives you've considered

I'm currently identifying each manifest by hand and using skopeo manually. I'm blocked from using the resultant .tar.gz file in zarf though due to #2181

Additional context

Related note from the zot container registry report: project-zot/zot#2234