Switch peer keys over to Ed25519

[dlongley]

We should switch to Ed25519 as soon as we can (prior to testnet launch preferably) for peer keys. There's no compatibility need for RSA and we only need a node.js implementation (no need for a browser implementation). Essentially, there's no reason not to switch, only advantages.

[mattcollier]

This has already been implemented, but I have just discovered a wrinkle. I believe the plan was to utilize HTTP Signatures to secure the gossip endpoints to allow requests only from authorized peers.

I found this PR which you may be familiar with: TritonDataCenter/node-http-signature#58 and digitalbazaar/request@f3cdbc2

It does not appear that there is any support for ed25519 in the http-signatures module.

Does something need to be done that works with the RequestSigner API?

[dlongley]

Yeah, I think we'll have to use the RequestSigner API and create the headers separately and pass them manually to request (or r2).

[mattcollier]

ed25519 has been implemented in continuity. Added issue for upgrading HTTPSignature support here: digitalbazaar/bedrock-passport#19