dillon1000/react

Suspended high pri work forces lower priority work to expire early (#12965)

* onFatal, onComplete, onSuspend, onYield

For every call to renderRoot, one of onFatal, onComplete, onSuspend,
and onYield is called upon exiting. We use these in lieu of returning a
tuple. I've also chosen not to inline them into renderRoot because these
will eventually be lifted into the renderer.

* Suspended high pri work forces lower priority work to expire early

If an error is thrown, and there is lower priority pending work, we
retry at the lower priority. The lower priority work should expire
at the same time at which the high priority work would have expired.
Effectively, this increases the priority of the low priority work.

Simple example: If an error is thrown during a synchronous render, and
there's an async update, the async update should flush synchronously in
case it's able to fix the error. I've added a unit test for
this scenario.

User provided timeouts should have the same behavior, but I'll leave
that for a future PR.