Add a sub-command group to podman machine called 'os'.  The group should be disabled or hidden as well as the corresponding files in cmd/podman with a build tag.

Manage a virtual machine OS
Description:  

  Manage the operating system of a machine
Usage:  

  podman machine os [command]

Available Commands:  

apply         Apply a new machine image and reboot machine  

build         Build a new machine image from a Containerfile  

revert        Reboot to the previous machine image