leaudio: Fix assigning bidirectional CIS to ASE for TWS headset.

Failure happens when restarting conversational scenario and when
remote device uses caching.

Failing scenario.
1. Conversational scenario set up with
 - ASE 1 and ASE 5 using bidirectional CIS 0
 - ASE 2  being unidirectional on CIS 1
2. Stop stream and go to CONFIGURED STATE.
3. Trying to configure ASES again would end up in incorrectly assigned
   CISes
 - ASE 1 and ASE 5 set to CIS 0
 - ASE 2 stay on CIS 1 but ASE 5 got reassigned to CIS 1 (error)

The problem is finding matching_bidir_ase which shall not be just next
active ase with different direction, but it shall be also available (Cis
not assigned) or assigned to the same CIS ID as the opposite direction.

This patch fixes that.

Tag: #feature
Bug: 266417518
Test: atest --host bluetooth_le_audio_test bluetooth_le_audio_client_test
Change-Id: I1027f0a79da35ed0b31995e1d7f2337f8d8da6f5