Raise Exceptions to AIDE UI via metadata.json

[tomaroberts]

Currently, to debug on AIDE, the user must go through the log file, which is lengthy and the formatting is not ideal. A better way to surface Exceptions would be used the metadata.json functionality within MONAI Deploy/AIDE.

See here: https://github.com/Project-MONAI/monai-deploy-workflow-manager/blob/develop/guidelines/mwm-workflow-spec.md#handled-exception-metadata

Example Exceptions (off top of my head) to raise:

• No segmentations produced
• NIfTI files problematic
• Issue with Clinical Review PDF
• etc.