le_audio: Use bi-directional scenario for ringtone for ringtone

Patch adds bi-directional scenario for ringtone to avoid
re-configuration while progressing to conversational - answer call.

Bug: 233961821
Tag: #feature
Sponsor: jpawlowski@
Test: atest bluetooth_le_audio_test
Test: atest bluetooth_le_audio_client_test
Change-Id: Ic450fa8e6ef1c1c26e1e507f636b45505f6b249e