dillon1000/react

[Fiber] Support React DevTools (#8818)

* Initial React DevTools support for Fiber

* Record a newly failing irrelevant test

This is fine because we don't use it in Stack anyway (at least not that part), and we also rely on Set/Map in other parts of code.
The newly failing test is the one saying "it works without Map/Set".

* Explicitly check for Fiber DevTools support

This lets us ignore pre-Fiber DevTools instead of crashing them by injecting a different API.

* Track the roots in DevTools instead

* Lol Dan this is not how warnings work in our codebase

* Move injection to the renderer

* Notify DevTools about unmounts

* Make it work in production

* Fix lint and flow

* Fixups

* Address feedback