GitLab

* Add enrollment status to proto
* Remove stages not handled by HostPairingController, and ControllerPairingController.
* UpdateScreen sends update status via remora_controller.
* EnrollmentScreen sends enrollment status via remora_controller.
* Remove auth_token_ from EnrollmentScreen.
* Rename to shark_controller and remora_controller in WizardController.
* Remove get_initial_status_ from BluetoothControllerPairingController.

Review URL: https://codereview.chromium.org/652743003

Cr-Commit-Position: refs/heads/master@{#299422}