[WIP] support forthcoming "any" facility

[vielmetti]

At Packet we are considering on an API update that will would users to choose “any” or “first available” as a facility location. This work is not done yet, but the idea is that it would simplify location selection for test deployments where you are willing to pick from available inventory more independently of location.

This would probably show up in the packet baremetal create-device --facility command but there may be other places it touches.

I'll update this issue when the code is ready to test and the docs are written.