LeAudio: Respond to TMAP read requests

* Supported roles are Call Gateway and Unicast Media Server
* Broadcast roles depend on runtime flag
* Also implemented a simple unit test
* Use objects factory in LeAudioService

Bug: 150670922
Bug: 229045392
Sponsor: @jpawlowski
Test: atest BluetoothInstrumantationTests
Change-Id: I91d6febda6ae080a5f6027312ec34e2e598d2a68