Fix nested wrappers bug in react-testing

[cartogram]

This PR fixes a bug in react-testing where an unresolved promise required an additional act() around the state change.

[lemonmade]

Hmm, I'm not sure I understand why you would do it here, also. if the result is a promise, there shouldn't be a reason to update until after the act block has finished, is there?

[marutypes]

If the function you triggered looks something like

async function doASubmit() { 
   setSomeLoadingState(true);
   await sendSomeRequest();
   setSomeLoadingState(false);
}

Then after synchronous execution pauses on the await there has been a state update, if we don't call updateWrapper then any test for loading states in cases will fail.

[lemonmade]

For this to make sense, setSomeLoadingState has to run synchronously. I don't think that's guaranteed for async functions?

[lemonmade]

Resolved in Slack, we agreed that this is probably the expected behaviour, and if they need to wait until any other update is finished and then update the tree, they can do so with act

[cartogram]

@lemonmade @TheMallen updated the PR to do 2 things:
1) made the update option for act is an enum of Pending, Complete or Never. The default is still Complete as before, but now we can offer somewhere for users to configure this from their tests.
2) expose the update method publicly on the root so that users can call the wrapper.update() after a loading state is triggered and then assert on the updated UI.

Update: I removed those and still going with what I had initially.

[lemonmade]

Resolved in Slack, we agreed that this is probably the expected behaviour, and if they need to wait until any other update is finished and then update the tree, they can do so with act