1. Use flag to control the UI migration
2. Create language_and_region_settings.xml for new UI migration.
Bug: 379962955
Flag: com.android.settings.flags.regional_preferences_api_enabled
Test: check hsv and atest LanguagePreferenceControllerTest
Change-Id: If8d2303a2a3061231e69d1a45ad432c061da3545
1. Separate "Keyboard" from "Language & input".
2. Use FeatureFlagUtils.SETTINGS_NEW_KEYBOARD_UI to control the
different UI until Settings launches the new UI design.
Bug: 242680328
Test: local test
Change-Id: Id1ea6d3e3c2e6b83bc4b4d835c6b27e31311c530