-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
-Add group operation slice to edit the group and do the volume adjustment
-Add grouping API in slice worker
-Add test cases
Bug: 146813761
Test: make -j42 RunSettingsRoboTests
Change-Id: Ide0df5e3934bc8ac68aaa67fcbd6173a4454ac7f