le_audio: Implement group direction handling

Patch implements handling of group direction member. While device
location is updated, group direction should be also. If some of device
would be added or removed from group, group direction should be also
updated.

Test: atest bluetooth_le_audio_client_test
Sponsor: @jpawlowski
Bug: 229802353
Change-Id: I3439786de6286ad1eaa82254709a3fd725a95dc5