dillon1000/react

[SuspenseList] Store lastEffect before rendering (#17131)

* Add a failing test for SuspenseList bug

* Store lastEffect before rendering

We can't reset the effect list to null because we don't rereconcile the
children so we drop deletion effects if we do that.

Instead we store the last effect as it was before we started rendering
so we can go back to where it was when we reset it.

We actually already do something like this when we delete the last row
for the tail="hidden" mode so we had a field available for it already.