LeAudio/CodecExtensibility: Use proper allocated channel counts

The channel count should not be hard-coded, but use the channel
allocation bitmask.

Bug: 308428644
Bug: 313054645
Test: atest bluetooth-test-audio-hal-le-audio-software bluetooth-test-audio-hal-aidl-leaudio-utils bluetooth_le_audio_test bluetooth_le_audio_client_test bluetooth_test_broadcaster bluetooth_test_broadcaster_state_machine bluetooth_le_audio_codec_manager_test
Flag: com.android.bluetooth.flags.leaudio_multicodec_aidl_support
Change-Id: I54bab9050ba02bc88df988a3e3bd0a82d33b8ce2