Sagemaker Studio notebooks are broken

Both the sagemaker-studio example notebooks are broken. The framework mode xgboost example does not show any trial components on the studio, and the pytorch mnist example script is broken (multiple issues with logger, data reading, etc).

Start with both SageMaker Studio example notebooks and reproduce the framework-mode XGBoost trial-component problem in Studio. Then run the PyTorch MNIST example and trace the reported logger and data-reading failures; done means both examples run correctly and the XGBoost notebook shows trial components in Studio.

Written by the indexing model from the issue text.