Add cosign for handling image functionality.

[amartin120]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Replaces default hauler image mechanics with cosign.
• Pulls in the once separated rancherfederal/OCIL library for the remaining oci functions not handled by cosign.

• What is the current behavior? (You can also link to an open issue here)

• When you add an image, that's it. No other supported artifacts come with it.
• Does not work for multi-arch images.

• What is the new behavior (if this is a feature change)?
  When you add an image to the store, it will also attempt to include any signatures/attestations.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)

• Other information: