Convert ready operations to promises.
Review Request #2376 — Created Dec. 11, 2021 and submitted
This change updates the `ready` method to use promises and async/await instead of callbacks. This flattens almost all of our remaining asynchronous operations. Testing Done: - Ran js-tests. - Smoke tested various UI functionality. Reviewed at https://reviews.reviewboard.org/r/11842/
done testing, no probelm