Removes `testenv` annotations and related code. These annotations originally let you skip x-pack snippet tests in the docs. However, that's no longer possible.
Relates to #79309, #31619
* First crack at rewriting the CCR introduction.
* Emphasizing Kibana in configuring CCR (part one).
* Many more edits, plus new files.
* Fixing test case.
* Removing overview page and consolidating that information in the main page.
* Adding redirects for moved and deleted pages.
* Removing, consolidating, and adding redirects.
* Fixing duplicate ID in redirects and removing outdated reference.
* Adding test case and steps for recreating a follower index.
* Adding steps for managing CCR tasks in Kibana.
* Adding tasks for managing auto-follow patterns.
* Fixing glossary link.
* Fixing glossary link, again.
* Updating the upgrade information and other stuff.
* Apply suggestions from code review
* Incorporating review feedback.
* Adding more edits.
* Fixing link reference.
* Adding use cases for #59812.
* Incorporating feedback from reviewers.
* Apply suggestions from code review
* Incorporating more review comments.
* Condensing some of the steps for accessing Kibana.
* Incorporating small changes from reviewers.
Co-authored-by: debadair <debadair@elastic.co>
Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
