Cloud-Init support for amd64 (PC/Desktop)

Reference: https://cloudinit.readthedocs.io/

Config files are installed to /var/lib/cloud/seed/nocloud/ which is the
standard NoCloud datasource seed directory for non-RPi systems.

- files/network-config      Network configuration template (netplan format)

- files/user-data           Example user-data configuration

- files/meta-data-amd64     Cloud-init instance config (instance_id: vesperos-image)

The NoCloud datasource is used so cloud-init picks up config from the local
seed directory on first boot without requiring a network metadata service.
