Add more of the musig spec tests

[LLFourn]

A few new musig spec test type have been added. We should test against them.

See: https://github.com/jonasnick/bips/tree/musig2/bip-musig2/vectors

and look how the python code uses the json files. Currently we have:

  key_agg_vectors.json
  sign_verify_vectors.json
  tweak_vectors.json

Some of the ones provided are not applicable since we handle nonce generation in a different way but I think we could test against some of the others.