Upgrade CLI and Metro, update status check refs (#38988)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/38988

- Upgrade to RN CLI `12.0.0-alpha.9`, including Metro bump to `0.78.0`.
- Update test scripts, since this CLI release made a breaking change to the `/status` response.

Changelog: [Internal]

Reviewed By: cortinico

Differential Revision: D48311214

fbshipit-source-id: bb0be3c32edb629355b9fbbd754b28f9878f47ef