Add the explicitly mutable flag for creating a PendingIntent

- Android S+ to specify explicitly either FLAG_MUTABLE or FLAG_IMMUTABLE
  when creating a PendingIntent.
- Suggest to use the FLAG_IMMUTABLE as default. Change it to
  FLAG_MUTABLE while errors occur.

Fixes: 170162598
Fixes: 170162878
Fixes: 170163592
Fixes: 170164316
Fixes: 170164458
Fixes: 170164327
Fixes: 169794524
Fixes: 170165106
Test: build pass, manual test add an account and volume control panel
Change-Id: I5aec028f82bd74fc4530b95a7c144811055ae2c5

src/com/android/settings/location/LocationSlice.java

@@ -96,6 +96,6 @@ public class LocationSlice implements CustomSliceable {
     private PendingIntent getPrimaryAction() {
         final Intent intent = getIntent();
         return PendingIntent.getActivity(mContext, 0 /* requestCode */,
-                intent, 0 /* flags */);
+                intent, PendingIntent.FLAG_IMMUTABLE);
     }
 }