[camera] Reland implementation of flip camera while recording. App facing changes

[BradenBagby]

This is the final PR for the app facing camera package for the original flip/change camera PR on the old Plugins repo here: https://github.com/flutter/plugins/pull/6478

The application interface was merged here: https://github.com/flutter/plugins/pull/7011 The platform packages were merged here: https://github.com/flutter/packages/pull/3460