Add ebsnvme-id to EC2 AMIs and enable /dev/aws/disk

Add ebsnvme-id to EC2 AMIs and enable /dev/aws/disk

The ebsnvme-id utility exposes information about EC2 disks -- for
Elastic Block Store volumes, their volume IDs and "linux device
names", and for Instance Store (aka "Ephemeral") disks, their
serial numbers.

The dev_aws_disk rc.d script and associated devd.conf rule maintains
a tree under /dev/aws/disk:
	/dev/aws/disk/ebs/<volume ID>
	/dev/aws/disk/linuxname/<linux device name>
	/dev/aws/disk/ephemeral/<serial number>
which are symlinks to the corresponding nda or nvd devices.

MFC after:	1 week
Sponsored by:	https://www.patreon.com/cperciva