Fetch bootstrap peers from dnsaddr records

[algoanne]

Problem

An algod node needs to be able to pull down and recursively resolve entries in dnsaddr records for use in the p2p network code.

Solution

Algod can fetch either static or DNS-based TXT records.
Algod can then read the records to produce Peer IDs, Addrs (IP address), and protocols (which protocol the peers are using - likely websocket) which are encoded and matched in the records.

For testing, we could use existing DNS infra (algodev.network) and augment it, or just use a text file on the host to mock it.