Add a WidgetsSearchBar(Launcher3) and a WidgetsSearchController.

- Make WidgetsSearchBar in Launcher3 initialize WidgetsSearchController with SimpleWidgetsSearchPipeline
- Modify SimpleWidgetsSearchPipeline to filter widgets entries on widgets/shortcut labels also.

Test: Tested prototype locally. Also added robolectric test.
Bug: b/157286785
Change-Id: I65f5fa0240ffb6d22023167e4e86d94d83bbd9f7

src/com/android/launcher3/search/SearchAlgorithm.java

@@ -31,4 +31,9 @@ public interface SearchAlgorithm<T> {
      * Cancels any active request.
      */
     void cancel(boolean interruptActiveRequests);
+
+    /**
+     * Cleans up after search is no longer needed.
+     */
+    default void destroy() {};
 }