Add support to generate OCI compatible output for orabos

[NotTheEvilOne]

What this PR does / why we need it:
This PR adds image.oci to orabos to generate OCI output for consumption.

Release note:

Adds support to generate OCI compatible output for `orabos`

[toanju]

Shouldn't this be a dedicated feature rather than in orabos ?

[NotTheEvilOne]

Thanks for your feedback. Unfortunately the feature _oci does more than what you would expect (see README.md of the feature) and need to be adjusted therefore. I'll give feedback on that upstream.

[toanju]

closing in favor of #36