Add XRDeficitModel for xarray LUT-based deficit models + remove optional...

docs/notebooks/exercises/CombineModels.ipynb

docs/notebooks/exercises/Validation.ipynb

py_wake/deficit_models/deficit_model.py

py_wake/deficit_models/fuga.py

py_wake/deficit_models/noj.py

py_wake/tests/test_deficit_models/test_XRDeficitModel.py

py_wake/tests/test_utils/test_model_utils.py

py_wake/utils/model_utils.py

py_wake/wind_farm_models/engineering_models.py