Extract RCTRedBoxController from RCTRedBox.mm (#56509)

Summary:
Pull Request resolved: #56509

Moves the `RCTRedBoxController` class, previously inlined in `RCTRedBox.mm`, into its own implementation and header files (`RCTRedBoxController.mm`, `RCTRedBoxController+Internal.h`). An upcoming diff will fork these files for the experimental RedBox 2.0.

Changelog: [Internal]

Reviewed By: christophpurrer

Differential Revision: D101484586

fbshipit-source-id: 0b0c80caa790ee5286c48adfce5c22d22bef47b6

Author: motiz88