[DOCS] Rollup refactor docs

[jrodewig]

This meta issue tracks documentation efforts for the rollups refactor (AKA rollups v2).
To monitor ongoing development, see #42720.

To Do:

• Document rollup API [DOCS] Add rollup V2 API docs #65398
• Update rollup security privileges [DOCS] Add rollup V2 security privileges #65512
• Document ILM rollup action Add Rollup ILM Action #65633, [DOCS] Document ILM rollup action #67108, [DOCS] Reuse ILM rollup action config #68755
• Update rollup overview. Add redirects as needed. (https://github.com/jrodewig/elasticsearch/tree/docs__rollup-v2-overview)
  • Add xref for overview page to legacy rollup API admon [DOCS] Add xrefs to rollup overview #68119
  • Add xref to rollup glossary item [DOCS] Add xrefs to rollup overview #68119
• Update rollup glossary items [DOCS] Update rollup glossary item #65519
• Label legacy rollup APIs and add a deprecation warning. [DOCS] Label legacy rollup APIs #65518
• Add support for multiple rollup configs
• Rollup migration API
• Note migrated rollup indices do not support automatic search resolution
• Note ES does not apply index templates to rollup indices
• Note runtime fields are not supported (in original index or search). Need to confirm.
• Release notes and highlights:
  • Update 8.0 breaking changes for legacy rollups [DOCS] Note StartRollupJob breaking change applies to legacy rollup jobs #66894
  • Document legacy API deprecation in breaking changes/migration guide (https://github.com/jrodewig/elasticsearch/tree/docs__rollup-deprecation)
  • Document new rollup functionality in release highlights (https://github.com/jrodewig/elasticsearch/tree/docs__rollup-release-highlights)
• UI changes:
  • Update reference in Index Management docs
  • Remove and/or combine the Kibana rollup jobs docs
  • Differences between V2 and historical rollups

Clean up before release:

• Remove feature flag from docs integ test (c.f. [DOCS] Add rollup V2 API docs #65398)
• Remove permanently-unreleased-branch conditionals
• Update 7.x references to the actual release:
  • Rollup APIs: https://www.elastic.co/guide/en/elasticsearch/reference/master/rollup-apis.html#legacy-rollup-apis
  • Deprecation note: https://www.elastic.co/guide/en/elasticsearch/reference/master/rollup-put-job.html

[elasticmachine]

Pinging @elastic/es-docs (Team:Docs)

[elasticmachine]

Pinging @elastic/es-analytics-geo (Team:Analytics)

[jrodewig]

We've decided to adopt a new approach for the rollup refactor.

I'm rolling back this work with #70885 and closing this issue.