dillon1000/react

Fix: Update while suspended fails to interrupt (#26739)

This fixes a bug with `use` where if you update a component that's
currently suspended, React will sometimes mistake it for a render phase
update.

This happens because we don't reset `currentlyRenderingFiber` until the
suspended is unwound. And with `use`, that can happen asynchronously,
most commonly when the work loop is suspended during a transition.

The fix is to make sure `currentlyRenderingFiber` is only set when we're
in the middle of rendering, which used to be true until `use` was
introduced.

More specifically this means clearing `currentlyRenderingFiber` when
something throws and setting it again when we resume work.

In many cases, this bug will fail "gracefully" because the update is
still added to the queue; it's not dropped completely. It's also
somewhat rare because it has to be the exact same component that's
currently suspended. But it's still a bug. I wrote a regression test
that shows a sync update failing to interrupt a suspended component.