LeAudio: QoS configurations improvements

Since the 'target_latency` is a QoS type of parameter, it should be
moved into the QoS section. This makes the codec configurations
ortogonal to QoS, allowing us to reuse the same codec configuration
with different 'target_latency', without the need to copy the whole
configuration just to change this one parameter.

It will also prevent invalid configurations where HighReliability
'target_latency' is paired with QoS settings for low latency stream.

Lastly the naming now explicitly states if the server preference that
we ask the remote device for is low latency, balanced realiability or
high reliability mode.

Bug: 269394021
Tag: #feature
Test: atest --host bluetooth_le_audio_client_test bluetooth_le_audio_test --no-bazel-mode
Change-Id: I4774591252e1479dc0712afbf9f7f7ba0aa8ca35