enhance: Experimental fetcher resolves before react render

[ntucker]

Motivation

Part of #760

This makes little difference in React 18 since renders are batched; however in React < 18, this means that code after promise resolution will be executed before react renders - allowing actions that need to take place as a result of successful fetch. For example navigating off a deleted page after delete.

Solution

Using promise chaining allows us to order microtasks so the resolution of useFetcher()'s promise happens before dispatch of receive.

This has many consequences for existing behaviors so we are opting in via the new fetch mechanism.

It's now recommended to wrap all fetches in act when testing like so:

    await act(async () => {
      await result.current.fetch(ComplexResource.detail(), {
        id: '5',
      });
    });

[ntucker]

@sweetro