leaudio: Clear CIS ID allocation when group goes to IDLE

If CIS ID are cleared on CIG Remove, but ASE are cached and stay in
configured state, state machine cannot go directly to QoS Confing
because CIS ID might change.
With this patch, CIS ID are also cached in case group stays in
Configured state

Bug: 222674521
Bug: 150670922
Test: atest --bluetooth_le_audio_test bluetoot_le_audio_client_test

Change-Id: Ia785af19404bd90c28abf1fb4d22c4b40a2e3135