Fix incorrect 16_2 configuration selection based on capabilities order

* The design prioritizes configurations in the stack as follows: 48_4 > 48_2 > 24_2 > 16_2
* Previous logic could incorrectly select 16_2 if it appeared first in the capabilities list.
* Includes minor refactoring for code redability improvement.

Bug: 329134305
Bug: 316005152
Test: atest bluetooth_le_audio_codec_manager_test
Change-Id: Iaeec8ed5e1593d87f9714662abfdfe75f1e8d3db