Declare official platform slice

Create the notion of an official platform slice.
This includes:
- Adding a second authority to the provider
- tagging slices in xml with a platform slice flag
- Including authority in the getUri method

Bug:73359139
Test: robotests
Change-Id: I5382be138a262dbc5a8324c34aab131c5d0d5516
Merged-In: I581ee6dfcdf935f452a15e89e5d055e375ff1877
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index dbe231b..f1bb595 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -3218,7 +3218,7 @@
         </activity>
 
         <provider android:name=".slices.SettingsSliceProvider"
-                  android:authorities="com.android.settings.slices"
+                  android:authorities="com.android.settings.slices;android.settings.slices"
                   android:exported="true">
         </provider>