dillon1000/react

root.createBatch (#11473)

API for batching top-level updates and deferring the commit.

- `root.createBatch` creates a batch with an async expiration time
  associated with it.
- `batch.render` updates the children that the batch renders.
- `batch.then` resolves when the root has completed.
- `batch.commit` synchronously flushes any remaining work and commits.

No two batches can have the same expiration time. The only way to
commit a batch is by calling its `commit` method. E.g. flushing one
batch will not cause a different batch to also flush.