Remove LocalePickerWithRegion class in Settings.

This class is too complex, we can't afford maintaining this long term.
We need a new Activity that wraps the framework version of LocalePickerWithRegion.

Bug: 111373939
Test: manual test & make RunSettingsRoboTests -j56

Change-Id: I93c719246b84350d2eee4e8ce1ffd97cd168925b