Allow 'gs' to Specify Gather-Scatter Kernel

[radelja]

Overview

This PR updates the command-line parsing to allow both 'gs' and 'sg' to specify the gather-scatter kernel. The argument parsing for JSON files already supports both of these options.

✨ Change Description/Rationale

• Gather-Scatter kernel can now be specified with 'gs' from the command-line
• Closes #217

👀 Reviewer Checklist

• [ ] All GitHub actions and runners have passed if applicable
• [ ] Commits are clean and relevant

✅ PR Checklist

• [x] Remove or update the template boilerplate text
• [x] Commits are relevant and combined where appropriate
• [x] Rebase off spatter-devel
• [x] Reviewers Requested
• [ ] Projects associated
• [x] Commits mention issue and/or PR numbers at the bottom of the message
• [x] Relevant issues are linked into the PR
• [ ] TODOs are completed
• [ ] Reviewer checklist is updated

🚀 TODOs

• [ ] No additional TODOs for this PR

📌 Future Work

• No additional future work