Fix comms benchmark import issues and support MPI/slurm launching (#2932)
* Fix benchmark import issues and support MPI launching with pure torch.dist
* Formatting
* Update comms benchmark README
* Formatting
* Added better error handling and support MPI torch.dist backend
* Update formatting versions
* Formatting again
* Trigger CI
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Co-authored-by: Jeff Rasley <jerasley@microsoft.com>