Add MULTICHANNEL_SPEAKER_GROUP to MediaRoute2Info

The MULTICHANNEL_SPEAKER_GROUP route is a wired system route. It's using
audio device AudioDeviceInfo.TYPE_MULTICHANNEL_GROUP for playback.

Flag: android.media.audio.enable_multichannel_group_device
Bug: 344031109
Test: atest CtsMediaBetterTogetherTestCases CtsMediaHostTestCases
Change-Id: Icbd2509c125ace159123ccc36a11562fc78651fe