Removing Ethernet address from version 1 UUIDs

[baarde]

Using the Ethernet address in time-based (version 1) UUIDs has several caveats:

• Determining the Ethernet address is not portable. The current implementation requires to embed C code in the library and only supports Darwin and Linux.
• The Ethernet address is not always globally unique.
  • On a MacBook Pro with touch bar, the first network interface is always ac:de:48:00:11:22.
  • Docker assigns Ethernet addresses from the range 02:42:ac:11:00:00–02:42:ac:11:ff:ff.
  • And there are probably more example.
• Exposing the Ethernet address may leak private information.

We already use a random node identifier as a fallback when the Ethernet address cannot be determined, as specified in RFC 4122 section 4.5. I suggest we make using that random identifier the default choice for UUID.v1.