[various] Simplify testing, metadata saving, json data saving

src/mednet/libs/classification/engine/evaluator.py

src/mednet/libs/classification/scripts/evaluate.py

src/mednet/libs/classification/scripts/experiment.py

src/mednet/libs/classification/scripts/predict.py

...dnet/libs/classification/scripts/saliency/completeness.py

src/mednet/libs/classification/scripts/saliency/generate.py

.../libs/classification/scripts/saliency/interpretability.py

src/mednet/libs/classification/scripts/saliency/view.py

src/mednet/libs/classification/scripts/train.py

src/mednet/libs/classification/scripts/upload.py

src/mednet/libs/common/scripts/predict.py

src/mednet/libs/common/scripts/train.py

src/mednet/libs/common/scripts/utils.py

src/mednet/libs/segmentation/scripts/dump_annotations.py

src/mednet/libs/segmentation/scripts/evaluate.py

src/mednet/libs/segmentation/scripts/experiment.py

src/mednet/libs/segmentation/scripts/predict.py

src/mednet/libs/segmentation/scripts/train.py

tests/classification/test_cli.py

tests/segmentation/test_cli.py