[Neo] Add Neo Neuron entrypoint script

[a-ys]

Description

This PR adds an entrypoint script that enables the LMI Neuron (pytorch-inf2) container to be used by SageMaker Neo to AOT compile models. This script does not modify default djl-serving behavior.

Changes to djl-serving code

• A check is added to model_loader.py to check if the partitioning output directory is mounted before calling rmtree() on it, which would cause an error.
• Added an optional "addl_properties" kwarg field to Partition PropertiesManager to enable passing model properties without parsing through serving.properties.