1. Proposed title of this feature request

> Include --keep-younger-than and --keep to oc adm prune renderedmachineconfigs

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

Currently, the only options for the MC prune is "everything" or "x oldest". If you run it in a daily cron, that will eventually delete all unused ones. It would be great to just keep all MC generated in the past 7 days, or keep the past 5 revisions of the MC and delete all the rest.

4. List any affected packages or components.