Prysm support

[dknopik]

Support the Prysm consensus layer client and validator client.

Current issue:
Here, prysm tries to get the "external ip". This is unavoidable. https://github.com/prysmaticlabs/prysm/blob/4386c244e1680d90ed3cc8123f453badf956efdd/network/external_ip.go#L49-L82
This ends up here with a deserialization failure: https://github.com/shadow/shadow/blob/4a1d8ac8d83266be2afa1f0c34fdc8a486688031/src/main/host/descriptor/socket/netlink.rs#L851-L855
I assume this is a bug in shadows netlink support.

[ppopth]

I was actually the one who implemented Netlink in Shadow 😄. I noticed already that net.InterfaceAddrs() doesn't work with my implementation. It's because the message formats sent by that Go function doesn't look compatible with the man page, but it's handled gracefully by Linux.

What I thought is Linux did it wrong, but I did it right, so I didn't care much. Maybe I should go and fix it.