le_audio: Implement handover to broadcast for Telecomm call and record

This CL adds autonomous switch to/from broadcast/unicast capability,
driven by TBS (Telecomm) API handled by LeAudioService and monitoring
Sink Bluetooth HAL session for e.g. recorder applications.

Tag: #feature
Test: atest LeAudioBroadcastServiceTest
Bug: 298079825
Bug: 308171251
Change-Id: I21ea2bb381c0fdabce358d02b026ecbd636eb04a