Add test vectors for mocked classes

[OR13]

In order to establish test vectors for EDVs we need to extract the string values from the mocked classes, and the expected inputs and outputs associated with hmac and ed25519 sign.

This PR adds JSON files for establishing conformance for mocked classes.

[OR13]

ping @dlongley @msporny @dmitrizagidulin trying to add test vector generation code to this code base, before attempting to reimplement the client for the SDS.

[OR13]

partially blocked by digitalbazaar/http-signature-zcap-invoke#11

[dlongley]

@OR13, ack, we're looking into the partial blocker.

[OR13]

This can be merged, and I can circle back to add better tests for http invocation if thats desirable.

[dlongley]

@aljones15 -- we need to run these test vectors against our current implementations to see if everything checks out. If it does, we can merge this -- if not, we should see what needs to be tweaked (one way or the other). I don't want to push test vectors forward that cause more people to have bugs/differences that shouldn't be there.

[OR13]

any movement on this?