Add isSliceable API to BasePrefController

Only support explicitly approved Settings Slices,
dictated by controllers which return true for the new
method isSliceable.

Updating the supported settings to a whitelist means that
the method to return all available slices must be updated,
and checking slicability when we index slices.

Test: robotests
Bug: 79779103
Change-Id: Ib2b9690cdd0036b5cc4a1cb846c52bce7c824ab9

src/com/android/settings/gestures/SwipeToNotificationPreferenceController.java

@@ -21,6 +21,7 @@ import static android.provider.Settings.Secure.SYSTEM_NAVIGATION_KEYS_ENABLED;
 import android.content.Context;
 import android.content.SharedPreferences;
 import android.provider.Settings;
+import android.text.TextUtils;
 
 import com.android.settings.Utils;
 
@@ -59,6 +60,11 @@ public class SwipeToNotificationPreferenceController extends GesturePreferenceCo
         return isAvailable(mContext) ? AVAILABLE : UNSUPPORTED_ON_DEVICE;
     }
 
+    @Override
+    public boolean isSliceable() {
+        return TextUtils.equals(getPreferenceKey(), "gesture_swipe_down_fingerprint");
+    }
+
     @Override
     public boolean setChecked(boolean isChecked) {
         setSwipeToNotification(mContext, isChecked);