Ability to sign driver containers images

1. Proposed title of this feature request
Container Image Signing for driver containers generated with SRO

2. What is the nature and description of the request?
When building a driver container there are two levels that need a signature. One is the kmod itself (which is NOT this request) and the other is the resulting driver container image (which is this request).

The details on the use case for this are illustrated here:

• https://www.openshift.com/blog/signing-and-verifying-container-images
• https://developers.redhat.com/blog/2019/10/29/verifying-signatures-of-red-hat-container-images#

3. Why does the customer need this? (List the business requirements here)

This capability is required for a drivers container to work on environments where OpenShift is configured to require signed images.