Separate "Keyboard" from "Language & input"

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
diff --git a/src/com/android/settings/Settings.java b/src/com/android/settings/Settings.java
index f1c1191..7ed95bc 100644
--- a/src/com/android/settings/Settings.java
+++ b/src/com/android/settings/Settings.java
@@ -111,6 +111,8 @@
     public static class SpellCheckersSettingsActivity extends SettingsActivity { /* empty */ }
     public static class LocalePickerActivity extends SettingsActivity { /* empty */ }
     public static class LanguageAndInputSettingsActivity extends SettingsActivity { /* empty */ }
+    public static class LanguageSettingsActivity extends SettingsActivity { /* empty */ }
+    public static class KeyboardSettingsActivity extends SettingsActivity { /* empty */ }
     public static class UserDictionarySettingsActivity extends SettingsActivity { /* empty */ }
     public static class DarkThemeSettingsActivity extends SettingsActivity { /* empty */ }
     public static class DisplaySettingsActivity extends SettingsActivity { /* empty */ }