prototype decentralized issuer naming using boardIds in agoricNames

[dckc]

The smart wallet will only make purses for issuers in agoricNames (Agoric/agoric-sdk#7226). We can't give everyone the right to register their token under a name of their choosing in agoricNames: they could register a worthless token as BTC.

But we can perhaps let people register tokens (issuers / brands) in agoricNames where the system chooses an arbitrary name for them.

And we might as well use board ids as the arbitrary names.

Tricky: names under issuer and brand usually correspond... should it be the brand boardID or the issuer boardID? my intuition says brand

[dckc]

@dtribble @Chris-Hibbert this is kinda motivated by swaparoo