Is your feature request related to a problem? Please describe.
In order to be able to support uploading models to OCI registries, ilab must first be able to convert the provided model into an OCI layout directory locally

Describe the solution you'd like
ilab should include logic that allows it to construct an OCI layout directory out of a supplied model directory. This functionality should be internally invoked within ilab model upload if user is targeting an OCI registry as the destination for upload.
This functionality should separately be exposed as an option via ilab model convert

The general workflow needed to be followed is:

• create a new local directory
• find the SHA for each file in the model dir, and rewriting the files into a blobs/ dir in the new directory
• add a manifest json in the blobs dir that references all model files via their SHAs and other required info
• create an index.json that references the manifest sha
• add an oci-layout file

Additional context