Adds CONTAINER_QSB to be used for QSB data.

Also updates some related generics definitions for
better/simpler compile-time checks.

Bug: 178536734
Test: Manual
Change-Id: If439b64ad968f62674f856fd3ff465bf21cc9204

src_plugins/com/android/systemui/plugins/BcSmartspaceDataPlugin.java

@@ -39,6 +39,6 @@ public interface BcSmartspaceDataPlugin extends Plugin {
     /** Provides Smartspace data to registered listeners. */
     interface SmartspaceTargetListener {
         /** Each Parcelable is a SmartspaceTarget that represents a card. */
-        void onSmartspaceTargetsUpdated(List<Parcelable> targets);
+        void onSmartspaceTargetsUpdated(List<? extends Parcelable> targets);
     }
 }