dillon1000/react

Event Replaying (#16725)

* Add Event Replaying Infra

* Wire up Roots and Suspense boundaries, to retry events, after they commit

* Replay discrete events in order in a separate scheduler callback

* Add continuous events

These events only replay their last target if the target is not yet
hydrated. That way we don't have to wait for a previously hovered
boundary before invoking the current target.

* Enable tests from before

These tests were written with replaying in mind and now we can properly
enable them.

* Unify replaying and dispatching

* Mark system flags as a replay and pass to legacy events

That way we can check if this is a replay and therefore needs a special
case. One such special case is "mouseover" where we check the
relatedTarget.

* Eagerly listen to all replayable events

To minimize breakages in a minor, I only do this for the new root APIs
since replaying only matters there anyway. Only if hydrating.

For Flare, I have to attach all active listeners since the current
system has one DOM listener for each. In a follow up I plan on optimizing
that by only attaching one if there's at least one active listener
which would allow us to start with only passive and then upgrade.

* Desperate attempt to save bytese

* Add test for mouseover replaying

We need to check if the "relatedTarget" is mounted due to how the old
event system dispatches from the "out" event.

* Fix for nested boundaries and suspense in root container

This is a follow up to #16673 which didn't have a test because it wasn't
observable yet. This shows that it had a bug.

* Rename RESPONDER_EVENT_SYSTEM to PLUGIN_EVENT_SYSTEM