[le audio] Get Broadcast quality based on selected output codec config

Get Broadcast Audio Quality based on selected output codec config
instead of input codec config for connected sink devices.

Bug: 370236114
Flag: EXEMPT; trivial fix covered by unit tests
Test: atest LeAudioBroadcastServiceTest
Test: manual testing with specific remote devices
Change-Id: Ibb9578e89e04eabc698b4fed947464153daa7958