dillon1000/react

Bugfix: Fix race condition between interleaved and non-interleaved updates (#24353)

* Regression test: Interleaved update race condition

Demonstrates the bug reported in #24350.

* Bugfix: Last update wins, even if interleaved

"Interleaved" updates are updates that are scheduled while a render is
already in progress. We put these on a special queue so that they don't
get processed during the current render. Then we transfer them to
the "real" queue after the render has finished.

There was a race condition where an update is received after the render
has finished but before the interleaved update queue had been
transferred, causing the updates to be queued in the wrong order.

The fix I chose is to check if the interleaved updates queue is empty
before adding any update to the real queue. If it's not empty, then
the new update must also be treated as interleaved.