Add entry point at output switcher to do group operation

-Entry point is available only when there are more than 1 connected device
-Add group Slice item when it is available
-Add intent filter in manifest
-Add test case

Bug: 146813761
Test: make -j42 RunSettingsRoboTests
Change-Id: If398b7a31219fd1910503d96fe7593622528c792

src/com/android/settings/media/MediaOutputGroupSlice.java

@@ -118,8 +118,7 @@ public class MediaOutputGroupSlice implements CustomSliceable {
         return listBuilder.build();
     }
 
-    private void addRow(ListBuilder listBuilder, List<MediaDevice> mediaDevices,
-            boolean selected) {
+    private void addRow(ListBuilder listBuilder, List<MediaDevice> mediaDevices, boolean selected) {
         for (MediaDevice device : mediaDevices) {
             final int maxVolume = device.getMaxVolume();
             final IconCompat titleIcon = Utils.createIconWithDrawable(device.getIcon());