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/notification/VibrateWhenRingPreferenceController.java

@@ -24,6 +24,8 @@ import android.database.ContentObserver;
 import android.net.Uri;
 import android.os.Handler;
 import android.provider.Settings;
+import android.text.TextUtils;
+
 import androidx.preference.Preference;
 import androidx.preference.PreferenceScreen;
 
@@ -63,6 +65,11 @@ public class VibrateWhenRingPreferenceController extends TogglePreferenceControl
         return Utils.isVoiceCapable(mContext) ? AVAILABLE : UNSUPPORTED_ON_DEVICE;
     }
 
+    @Override
+    public boolean isSliceable() {
+        return TextUtils.equals(getPreferenceKey(), "vibrate_when_ringing");
+    }
+
     @Override
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);