refactor: move to trade terminology

[h4sh3d]

Offer and negotiation are misleading as they are used to initialized a swap more than to negotiate a trade. To separate the current ambiguity we move completely to trade terminology to allow negotiation and offer to fulfill their roles later.

Also the negotiation is not part of the minimum stack and does not require to be inside core (nor even node), this can be left to other implementations.

EDIT

farcaster_core::negotiation becomes farcaster_core::trade
Offer becomes DealParameters
PublicOffer becomes Deal

[h4sh3d]

After some discussions we are moving from Trade to Deal because Trade and Swap are too close. The ideal flow would be

Offers (outside of scope)  --->  Deals  --->  Swaps

The cli would be able to list the registered deals and running swaps. A market maker would register deals and share them so takers can take deals.

[Lederstrumpf]

ACK, the language & terminology is consistent & sensible everywhere. I made some light adjustments in 8298692 - feel free to change those.

One place that this PR didn't touch is OfferString deserialization - I think that's a vestigial hack that can also be removed.

[Lederstrumpf]

One place that this PR didn't touch is OfferString deserialization - I think that's a vestigial hack that can also be removed.

git blame snitches that this was my dirt, and it's not used anywhere externally, so done in 1544847.