Ultralytics yolov8 QAT example

[alexsu52]

Create the QAT example based on ultralytics yolov8. The example should be added in examples/quantization_aware_training/torch/yolov8/

Motivation:

• Demonstrating NNCF QAT API
• Demonstrating the benefits of QAT
• https://github.com/openvinotoolkit/nncf/issues/2486

[avitial]

Ref. 138682