Add audio device type MULTICHANNEL_GROUP

Add audio device type MULTICHANNEL_GROUP for wireless speaker group
supporting multichannel content.

Flag: android.media.audio.enable_multichannel_group_device
Bug: 344031109
Test: atest CtsMediaAudioTestCases
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:a2d41f833cc2e3ce48f0ff7a5a7d04cfd2c65ce8)
Merged-In: If9ad55bd991f060c308dd128be489b51557a99e3
Change-Id: If9ad55bd991f060c308dd128be489b51557a99e3