dillon1000/react

Don't rely on `didTimeout` for SyncBatched (#19469)

Tasks with SyncBatchedPriority — used by Blocking Mode — should always
be rendered by the `peformSyncWorkOnRoot` path, not
`performConcurrentWorkOnRoot`.

Currently, they go through the `performConcurrentWorkOnRoot` callback.
Then, we check `didTimeout` to see if the task expired. Since
SyncBatchedPriority translates to ImmediatePriority in the Scheduler,
`didTimeout` is always `true`, so we mark it as expired. Then it exits
and re-enters in the `performSyncWorkOnRoot` path.

Aside from being overly convoluted, we shouldn't rely on Scheduler to
tell us that SyncBatchedPriority work is synchronous. We should handle
that ourselves.

This will allow us to remove the `didTimeout` check. And it further
decouples us from the Scheduler priority, so we can eventually remove
that, too.