Document `CIS-1.8` hardening guides and self-assessment-guides

[andypitcher]

CIS-1.8 parent issue: https://github.com/rancher/rancher/issues/43159

This issue is created to document the hardening guides and self-assessment-guides in Rancher docs for CIS-1.8 (rke1, rke2 and k3s).

[github-actions[bot]]

This repository uses an automated workflow to automatically label issues which have not had any activity (commit/comment/label) for 60 days. This helps us manage the community issues better. If the issue is still relevant, please add a comment to the issue so the workflow can remove the label and we know it is still valid. If it is no longer relevant (or possibly fixed in the latest release), the workflow will automatically close the issue in 14 days. Thank you for your contributions.

[andypitcher]

• [ ] K3s
  • https://docs.k3s.io/security/self-assessment-1.8
• [ ] RKE2
  • In progress
• [ ] RKE1
  • In progress