le_audio: Don't stop or cancel stream while being in inCall mode

In in-call mode, dynamic context changes (ringing -> conversation,
sound effects) can interrupt stream processing. This change adds a check
to prevent unintended group stops or sound effect cancellations.

Bug: 385380583
Bug: 376251433
Test: atest bluetooth_le_audio_client_test
Flag: com.android.bluetooth.flags.leaudio_stop_updated_to_not_available_context_stream
Change-Id: I9cc9ec6888f7271c2b59b1d7a82092702bec1436