Support SOCKS5 proxy

[3nprob]

For privacy-conscious users and enterprise environments alike, it' desirable or necessary with support for tunneling outgoing connections through a proxy.

This will also open the door for running avalanchego over Tor or I2P.

[github-actions]

This issue has become stale because it has been open 60 days with no activity. Adding the lifecycle/frozen label will cause this issue to ignore lifecycle events.