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
* [DOCS] Rework conceptual info for ILM.
* Split the actions out of concepts.
* Added xpack role to actions.
Co-Authored-By: James Rodewig <james.rodewig@elastic.co>
* Apply suggestions from code review
* [DOCS] ILM API Ref edits
* [DOCS] Fixed endpoint for DELETE policy.
* [DOCS] Removed comparison to setting index.lifecycle.name to null.
* [DOCS] Fixed xrefs to explain API.