le_audio: Handle multiple audio server tracks

Initial patch for handling multiple server tracks.
In this patch, if there is any track with voice communication purpose,
we add priority on it.

Bug: 150670922
Tag: #feature
Sponsor: jpawlowski@
Test: atest --host bluetooth_le_audio_test bluetooth_le_audio_client_test

Change-Id: I0ee8353b3ae304d5151ed4d2d860ca5f924b8ae7