mpirun protocol - distributed training with @remote decorator

[brunopistone]

Issue #, if available:

Description of changes: Introduced mpirun protocol for distributed training with multiple instances (instance_count > 1) with with remote decorator. mpirun protocol is the alternative to the torchrun protocol, introduced with PR merged #4984

Testing done: Unit tests mpirun single node with GPU, single node with multiple GPUs, multi node with multiple GPUs. Added new test cases for mpi_tuils_remote.py

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[benieric]

Is there any related documentation for remote decorator that should be updated for this change? under https://github.com/aws/sagemaker-python-sdk/tree/master/doc

had a question

[brunopistone]

Is there any related documentation for remote decorator that should be updated for this change? under master/doc

Classes are properly commented for having the documentation aligned with changes. This is the reference documentation (See use_torchrun parameter)