[FEATURE] Create a SOCI Index without a Container Runtime

[ollypom]

Description

Today the soci create command can only create a SOCI index from a container image that is stored locally to the soci client in a containerd image store.

soci-snapshotter/cmd/soci/commands/create.go

Lines 63 to 74 in db7df3a

	client, ctx, cancel, err := internal.NewClient(cliContext)
	if err != nil {
	return err
	}
	defer cancel()
	cs := client.ContentStore()
	is := client.ImageService()
	srcImg, err := is.Get(ctx, srcRef)
	if err != nil {
	return err
	}

However the SOCI Index Builder is able to generate a SOCI Index by first downloading and extracting a container image to a local arbitrary directory on the host using the ORAS library. Then it imports the logic from this repository to create the SOCI Index. Showing that its possible to generate a SOCI Index without a container runtime.

For CI/CD use cases it is often challenging to run a container runtime in a build job without adding additional privileges to the runner. So there is appetite to generate Indexes without any dependency on a container runtime, this has been shown by @kichik who has taken the logic out of the SOCI Index Builder into a standalone library https://github.com/CloudSnorkel/standalone-soci-indexer.

This feature request is to be able to build indexes without a container runtime either with the soci CLI or with a standalone binary.

Describe the solution you'd like

No response

Describe any alternative solutions/features you've considered

No response

Any additional context or information about the feature request

No response

[Kern--]

Related to #760