le_audio: Use audio recording callback to monitor recording

Simplifies handover triggering in LeAudioService by removing the use of
left-open sink sessions for monitoring during local broadcasting.

Bug: 349310336
Bug: 381054654
Test: atest bluetooth_test_broadcaster64
Test: atest LeAudioBroadcastServiceTest
Flag: com::android::bluetooth::flags::leaudio_use_audio_recording_listener
Change-Id: Ic457c24351faac41865af6ae5592b6e06f26227c