Bluetooth: Audio: Rename bt_audio_codec_qos -> bt_bap_qos_cfg

The QoS structure is not related to a codec, but rather a
stream, and should thus not use the "Codec" name.

The BAP and ASCS specs refer to the QoS as
"QoS configuration" several places, so it is an obvious
choice for a name.

Since the structure is defined and used by BAP, the prefix
was changed from bt_audio to bt_bap.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>