Use Kademlia DHT for peer discovery and storage

[binarybaron]

We should consider using a DHT (Distributed Hash Table) in addition to the rendezvous protocol for:

1. Peer discovery (specifically discovery of asbs) using Bootstrap
2. Content routing. We can store some information in the DHT in case we lose our connection to our trading partner. Specifically:
   • Alice can store transfer proofs in the DHT in case she loses her connection to Bob
   • Alice can store the s_a key in the DHT after she has punished Bob. This way Bob can recover the Monero at any time even long after Alice has gone offline
   • Bob can store the encrypted signature in the DHT
   • All entries should of course be encrypted such that only our trading partner can decrypt them

We might even be able to leverage IPFSs existing DHT network for this?

Relevant resources:

• https://pl-launchpad.io/curriculum/libp2p/dht/
• https://github.com/libp2p/specs/blob/master/kad-dht/README.md
• https://docs.rs/libp2p-kad/latest/libp2p_kad/