Backport ForceTorque system: improve readability (#2403)

[scpeters]

🦟 Bug fix

Backport of #2403 to Garden

Summary

Original description:

This adds some comments and uses structured bindings in range-based for loops to improve readability. It also adds const to unmodified variables in a loop.

Checklist

• [X] Signed all commits for DCO
• [ ] Added tests
• [X] Updated documentation (as needed)
• [ ] Updated migration guide (as needed)
• [ ] Consider updating Python bindings (if the library has them)
• [X] codecheck passed (See contributing)
• [ ] All tests passed (See test coverage)
• [ ] While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Rebase-and-Merge.