Specifies nav destination when opening shortcuts.

Doing this will open the correct screen when clicking on "Shortcuts"
under Settings > Display > Lock screen.

Fix: 258471384
Test: manually verified that clicking on it opens the wallpaper picker
experience with the correct page showing.

Change-Id: I627bcb9c9fac7a834f1c9d9cb36b73a6c8817af5

tests/robotests/src/com/android/settings/display/CustomizableLockScreenQuickAffordancesPreferenceControllerTest.java

@@ -102,6 +102,8 @@ public class CustomizableLockScreenQuickAffordancesPreferenceControllerTest {
         assertThat(intentCaptor.getValue().getPackage()).isEqualTo(
                 mContext.getString(R.string.config_wallpaper_picker_package));
         assertThat(intentCaptor.getValue().getAction()).isEqualTo(Intent.ACTION_SET_WALLPAPER);
+        assertThat(intentCaptor.getValue().getStringExtra("destination"))
+                .isEqualTo("quick_affordances");
     }
 
     @Test