Fix saving and loading model hyperparameters

src/ptbench/configs/models/pasa.py

src/ptbench/engine/callbacks.py

src/ptbench/models/alexnet.py

src/ptbench/models/densenet.py

src/ptbench/models/densenet_rs.py

src/ptbench/models/logistic_regression.py

src/ptbench/models/pasa.py

src/ptbench/models/signs_to_tb.py

src/ptbench/scripts/predict.py

src/ptbench/scripts/train.py