helper for async providing a value into a SharedStateRecord

[turadg]

What is the Problem Being Solved?

This is subject to race conditions:

agoric-sdk/packages/orchestration/src/examples/send-anywhere.flows.js

Lines 44 to 48 in ad7f655

	if (!contractState.localAccount) {
	const agoricChain = await orch.getChain('agoric');
	contractState.localAccount = await agoricChain.makeAccount();
	}

Multiple invocations of the same flow can concurrently find the localAccount to not be created yet, and attempt to create it.

Description of the Design

We need some provideOnce

Without membranes we’ve used makeAtomicProvider which takes a store and returns a provideAsync that uses a pending promises map to only try making each key once.

Security Considerations

Scaling Considerations

Test Plan

Upgrade Considerations

[mhofman]

IMO we should completely avoid the "shared state" record pattern unless the "provider" of the value is idempotent so that it can be invoked again in new incarnations because the "shared state" is not durable. And even then, I don't see why the "provider" cannot be directly endowed instead.