Backport path fixes for self-hosted docs sites to 16.8

What does this MR do and why?

Backports the fixes in !4598 (merged) to 16.8:

• Fixes Lunr search result URLs
• Fixes the link to the homepage from the logo
• Fixes the link to the latest version from the "archived version" banner

How to set up and validate locally

See !4635 (merged). Adjust version number accordingly.

Merge request acceptance checklist

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• I have evaluated the MR acceptance checklist for this merge request.