Avoid serving addresses of nodes which advertise outdated network protocol versions

[arya2]

Motivation

Zeeder currently uses NoChainTip when initializing zebra-network such that the handshake service will establish connections with peer nodes advertising outdated network protocol versions.

Design

• Export MockChainTip from zebra-chain
• Accept the current NU or network chain tip height/block-time as a CLI arg
• Use a mock chain tip with either the:
  • current NU activation height, or
  • the network chain tip height/block-time and a new zebra-network init fn that uses the estimated network chain tip height rather than the latest chain tip height to determine which network protocol version to expect from peer nodes.