Add descriptions to our documentation pages #911

We would like all (or most) of our documentation pages to have descriptions as they are useful for SEO/GEO and displayed as snippets in search results etc.

• docs: Add page descriptions to the Kubernetes, concepts and guides pages documentation#895
• chore: Move the resource requests fragment into a partial documentation#976
• Add descriptions to all repo docs pages
• Delete the resource request page and create a redirect.