Merge pull request #2546 from sebmarkbage/cleanupinternals

Move more stuff out of ReactComponent
Move ComponentEnvironment out of ReactComponent

We currently have three DOM specific hooks that get injected. I move those
out to ReactComponentEnvironment. The idea is to eventually remove this
injection as the reconciler gets refactored.

There is also a BackendIDOperation which is specific to the DOM component
itself so I move this injection to be more specific to the DOMComponent.

E.g. it makes sense for it to be injectable for cross-worker DOM operations
but it doesn't make sense for ART components.