Clear indexing before adding all Slices

Before we index, add a call to clear indexed data before
indexing again. It's an optional call.

Fixes: 80065409
Test: robotests

Change-Id: Iddb0ce02c50d84b51fbf6fc2be0bdc9aa1f5987a

src/com/android/settings/search/DeviceIndexFeatureProviderImpl.java

@@ -31,4 +31,9 @@ public class DeviceIndexFeatureProviderImpl implements DeviceIndexFeatureProvide
             List<String> keywords) {
         // Not enabled by default.
     }
+
+    @Override
+    public void clearIndex(Context context) {
+        // Not enabled by default.
+    }
 }