[scripts.evaluate] Complete refactor

src/ptbench/engine/evaluator.py

src/ptbench/engine/predictor.py

src/ptbench/models/alexnet.py

src/ptbench/models/densenet.py

src/ptbench/models/logistic_regression.py

src/ptbench/models/mlp.py

src/ptbench/models/pasa.py

src/ptbench/models/separate.py

src/ptbench/models/typing.py

src/ptbench/scripts/evaluate.py

src/ptbench/utils/download.py

src/ptbench/utils/grad_cams.py

src/ptbench/utils/image.py

src/ptbench/utils/measure.py

src/ptbench/utils/model_serialization.py

src/ptbench/utils/model_zoo.py

src/ptbench/utils/plot.py

src/ptbench/utils/table.py