Clean up public helper methods of SettingsValues

...rc/com/android/inputmethod/keyboard/KeyboardSwitcher.java

.../android/inputmethod/latin/AdditionalSubtypeSettings.java

...roid/inputmethod/latin/AudioAndHapticFeedbackManager.java

java/src/com/android/inputmethod/latin/LatinIME.java

...com/android/inputmethod/latin/RichInputMethodManager.java

java/src/com/android/inputmethod/latin/Settings.java

java/src/com/android/inputmethod/latin/SettingsFragment.java

java/src/com/android/inputmethod/latin/SettingsValues.java

.../com/android/inputmethod/latin/UserHistoryDictionary.java