[PK Setting] add keyboard review under keyboard selection page

Demo video as attached in bug.
Add new image view for keyboard layout review.
Reuse NewKeyboardLayoutPickerController under
NewKeyboardLayoutPickerFragment when get update for keyboard layout, get
preview image from inputManager and set to the view.

This feature will be guided with keyboard_layout_preview_flag, if the
flag is off, preview image from InputManager will be null.

Bug: 305588594
Test: Verified on device
Change-Id: Ic6f8e469d3cf7114dab6935304706ad42bf83608

src/com/android/settings/SettingsPreferenceFragment.java

@@ -479,7 +479,10 @@ public abstract class SettingsPreferenceFragment extends InstrumentedPreferenceF
                 mDialogFragment.dismiss();
                 mDialogFragment = null;
             }
-            getListView().clearOnScrollListeners();
+            RecyclerView view = getListView();
+            if (view != null) {
+                view.clearOnScrollListeners();
+            }
         }
         super.onDetach();
     }