Add dynamic navigation to RADIUSS Policies

[hauten]

Goal: Update Policies area of site with navigation like on Full catalog, where each subpage (e.g., Build) is navigable from the main page

• See original discussion in PR Introducing RADIUSS policies and guidelines #236
• Determine any necessary any design work (e.g., icons)
• Revert commit 0d66d32 (breadcrumbs currently in place)
• Make sure @adrienbernede has input