Migrate ChooseAccountActivity to DashboardFragment

- Build a controller to generate/manage a list of preferences.
- Move some logics to the controller and add tests.
- Rename to ChooseAccountFragment.

Bug: 73899467
Test: make RunSettingsRoboTests -j
      atest UniquePreferenceTest SettingsGatewayTest
Change-Id: Id2906c4b922ef159d08c803b976671264c54665f