Expose minor revisions of hardware plan via Metadata

This idea was imported from Canny. Originally created by: Daniel Lotterman. The current owner is: Unassigned.

An Equinix Metal "c3.medium.x86" can come in a couple of different form factors depending on luck at time of provision. Internally these different form factors are identified by a minor revision number, that is currently NOT exposed to the outside of the platform. Some of those revisions can introduce consequential changes to a customers ability to consume the service. Different drive types that will get named differently by the host OS, different NICs with different layouts etc. Without providing customers a way of keying of this information, it can present a significant challenge to customers trying to build auto-mateable / repeateable deployment patterns on Metal. We should expose the minor rev of the instance in Metadata, including the unathenticated metadata service. This would provide customers with a place to pivot instead of having to screen scrape the world and rebuild in it on-demand every time they want to in stall an OS.