expose VBANK brand list via chainStorage RPC

[dckc]

What is the Problem Being Solved?

The VBANK provides a subscription for new assets that includes a keyword/symbol and string name, but:

• it's not available via RPC (as noted in Naming hub: interface to look up an Issuer object and get a (set of) name(s) #5107 (comment) )
• it only gives the most recently added asset, where clients such as Guantlet and perhaps AMM want all current assets
• it doesn't include decimalPlaces

Description of the Design

pretty much implicit in the above

agoricNames should also be exposed via chainStorage RPC; it might be easier to roll that into this issue.

Security Considerations

Getting new assets into the VBANK is a privileged operation, currently reserved to the BLDer DAO. For a more decentralized approach, see wallet issues such as #5107.

Test Plan

unit tests for the items in the Description above

Demonstrate in econ testing: #5681

[dckc]

This might not be needed. @samsiegart and I just figured out a small tweak to the AMM contract:

• include the displayInfo (incl. decimalPlaces) in :published.amm.metrics.

If we make sure RPC chainStorage from each contract does this for its brands, we could perhaps do without it from VBANK.

We would lose the VBANK's string name (proposedName).

[dckc]

on further review, I can't figure out why this is necessary for #6021

[dckc]

brainstormed with @erights @michaelfig and @warner today... I think this is important for medium term work, though I don't suppose we came up with any hard requirement for it.

[dckc]

Motivation: currently the only way to find the vbank's name for a brand is to look it up via some user's wallet. What if you don't have a wallet address? You're just doing some chain-wide dashboard?

Well, I suppose you can pick one arbitrarily, but that sure seems awkward.