[EPIC] Unified Documentation Part 2

[pedro-psb]

The goal of this EPIC is to make the new Pulp Docs site production-ready and publish it under https://pulpproject.org/.

Community Post: https://discourse.pulpproject.org/t/unified-documentation-part-2/1188
Previous Epic: pulp/pulpcore#5037

First Step

• [CI] Add docs-build test on PRs CIs #31
• [misc] Gracefully deprecate legacy docs  #33
• [misc] Convert changelogs to markdown and change its generation #32 (rst repos)

Second Step

• [pulp-docs] Add more stable mechanism for ordering files/folders #20
• [pulp-docs] Add hot reload to pulp-docs serve #9
• [pulp-docs] Add Rest API and client bindings docs #40

Last Step

• [publish] Publish promote staging-docs.pulpproject to pulpproject.org
• [publish] Deactivate legacy docs and add redirects to pulpproject.org

Nice to Have

• [publish] Use latest released versions of each repository instead of main
• [content] General Review: fix internal links, image links, and general rendering issues (all repos)
• [pulp-docs] Improve Repository Map table (e.g, w/ correct versions)
• [pulp-docs] Add toc-summary on plugins index page (to get quicker overview of all content)
• [content] Main "getting started" tutorial
• [content] Installation docs in oci-images
• [content] Merge content from pulpproject.org into docs
• [pulp-docs] Add internal link checker #34
• [CI] As a doc-only contributor I would like to have the full CI skipped pulpcore#5085 (nice-to-have)