This change moves the NVIDIA IMEX Epilog and Prolog scripts out of the a4x blueprint into the slurm-gcp repo.
This significantly simplifies the a4x blueprint while keeping the practice consistent with a4high-slurm-blueprint.
The corresponding PR for slurm-gcp is : GoogleCloudPlatform/slurm-gcp#297

Submission Checklist

NOTE: Community submissions can take up to 2 weeks to be reviewed.

Please take the following actions before submitting this pull request.

• 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 #