Revise Containers section

[stevepiercy]

Here's a road map for reorganizing and revising the parts of the Containers section.

• Containers - Mix of Conceptual guide (introduction) and How-to (the rest of the page).
• Official Images - Each page is a mix of Reference (environment variables) and How-to, and should be split apart. I'd break each page into two.
• Examples of Plone 6 using containers - How-to. Add orchestration examples using Docker / docker-compose / Docker Swarm (and maybe other tools?).

Originally posted by @stevepiercy in https://github.com/plone/documentation/issues/1729#issuecomment-2460960816