feature: add python module entrypoint type, add python module support…

[clumsy]

Issue #, if available:

Related to aws/sagemaker-python-sdk#4324

Description of changes:
torchrun can run modules via -m <MODULE but SageMaker runtime does not yet support this entrypoint type. Adding a new entrypoint type and add support to torch_distributed.

Testing done:

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[emeraldbay]

LGTM

[emeraldbay]

LGTM

[clumsy]

Will create a new PR.