add support for Vows to smart-wallet

[turadg]

What is the Problem Being Solved?

Currently when an OfferResult is a promise, smartWallet awaits it with watchPromise to record the offer result.

agoric-sdk/packages/smart-wallet/src/offerWatcher.js

Lines 30 to 40 in fbd8633

	/**
	* @param {OutcomeWatchers} watchers
	* @param {UserSeat} seat
	*/
	const watchForOfferResult = ({ resultWatcher }, seat) => {
	const p = E(seat).getOfferResult();
	watchPromise(p, resultWatcher, seat);
	return p;
	};

Description of the Design

We could use watch in VowTools in place of the current watchPromises.

We might want to go further and use asyncFlow to refactor much of the smart wallet state handling.

Security Considerations

Scaling Considerations

Test Plan

Upgrade Considerations