ElligatorSwift "A/B" enum should have better-named variants

[apoelstra]

I think we can create a new enum, deprecate the old one, and use Into generics to make this a non-breaking change for most users.

[Kixunil]

Good idea, especially if you mean Into<NewEnum>.

[Davidson-Souza]

As the one to blame for this unfortunate naming, I agree that it should be clearer. The comments use "Initiator" and "Responder'. If you consider this is used in during a connection handshake, I think those makes sense.

[liamaharon]

Any suggestions for a more creative name for the new enum than ElligatorSwiftPartyV2?

[apoelstra]

I think we could shorten it to Party since it's in the ellswift module, the term "party" isn't used anywhere else, and with the long variant names it'll be better to have a short enum name.