Handle special case slices

Create a handler for any slice that doesn't include anything
from a PreferenceController.

Test: robotests
Change-Id: If23947152d61877537d0cac6240e96b9ab977bce
Bug: 80263568

tests/robotests/src/com/android/settings/slices/SettingsSliceProviderTest.java

@@ -109,6 +109,7 @@ public class SettingsSliceProviderTest {
         mProvider.mSliceWeakDataCache = new HashMap<>();
         mProvider.mSliceDataCache = new HashMap<>();
         mProvider.mSlicesDatabaseAccessor = new SlicesDatabaseAccessor(mContext);
+        mProvider.mCustomSliceManager = new CustomSliceManager(mContext);
         when(mProvider.getContext()).thenReturn(mContext);
 
         mDb = SlicesDatabaseHelper.getInstance(mContext).getWritableDatabase();