Play Nicely with The DOM Event System (because it's legacy anyway)

Currently React implements its own plugin system and event bubbling rules. This is important for systems like the responder system since the DOM event system is incapable of implementing proper event negotiation support. However, on desktop, we don't really take full advantage of our custom event system other than to polyfill mouseenter/leave and implement more bubbling. There are plenty of other things that are wrong with the DOM but instead of patching it, maybe it would be better to build a new view system on top of the DOM that integrates with the custom event system. Similarly to how React Native handles things. That way, the lowest level could just do what the DOM would do, however broken it may be. Question though: How do we handle things like onChange? cc @spicyj and @syranide since I know you always wanted this.