LeAudio: Send config updates to HAL on the active directions only

With this change, we will udpate the BT Audio HAL with the codec
configuration only on the directions which are about to be enabled and
used. This will avoid confusing the HAL about the stack intentions.

Bug: 386013408
Test: atest bluetooth_le_audio_client_test
Flag: Exempt; fix covered with unit tests
Change-Id: I763b32d08eab3b902abdc0b236373f74eaae040d