dillon1000/react

Avoid importing Scheduler directly (#14757)

* Avoid importing Scheduler directly

The reconciler should not depend directly on Scheduler. This adds it to
the host config for the renderer instead.

(Except for `scheduler/tracing` imports, which are used only by the
profiling build. I've left those imports as-is, though I'm open to
directing those through the host config, too.)

* Make throwaway root id longer to appease Brian