Propose: enable vyos cloud-init to have the same [disk_setup](https://cloudinit.readthedocs.io/en/latest/reference/modules.html#disk-setup) and [mount](https://cloudinit.readthedocs.io/en/latest/reference/modules.html#mounts) functionality as upstream cloud-init project, let vyos cloud-init able to setup additional disk(partition tables and filesystems), and mount the additional disk when boot.