This is a follow-up issue to #64944. Please see that issue for additional context.

This issue is about implementing step 2. from the overall plan outlined in #64944 (and potentially part of step 3. as well): All store actions should be yielded to the main thread, unless they use withEvent. At this point, data-wp-on-async should effectively be treated the same as data-wp-on, ignoring the difference between the directives, and data-wp-on-async should be discouraged as it no longer provides any value.

Since this is a breaking change, this must not happen until at least one release cycle after #64944 was launched in WordPress Core. We need to keep an eye out on ecosystem adoption of withEvent as well, before being able to confidently make this change.