leaudio: set preferred codec config conv test part 1

Adding unit test for api:SetCodecConfigPreference for all use case
before conv streaming

Bug: 259191520
Bug: 353909820
Flag: TEST_ONLY
Test: atest bluetooth_le_audio_test bluetooth_le_audio_client_test
Change-Id: Icbd04236e28f17327f2a61c4c4788b25e8bfc528