This speeds up the test duration, as well as resolves issues encountered between compatibility of spack-installed mpi/slurm w/ existing slurm enviornment.

Has been manually tested on a fresh a3u-slurm-ubuntu-gcs cluster.

Submission Checklist

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• Fork your PR branch from the Toolkit "develop" branch (not main)
• Test all changes with pre-commit in a local branch #
• Confirm that "make tests" passes all tests
• Add or modify unit tests to cover code changes
• Ensure that unit test coverage remains above 80%
• Update all applicable documentation
• Follow Cluster Toolkit Contribution guidelines #