This adds the _ilm/migrate_to_data_tiers API to expose the service for
migrating the elasticsearch abstractions (indices, ILM policies and an
optional legacy template to delete) to data tiers routing allocation
(away from custom node attributes)
* [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
Previously these were only linked in a circuitous way rather than being
available from the top level API documentation and "Put Lifecycle" API docs.
This makes them slightly easier to find for a user.
* [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.
Andrei Dan
James Rodewig
debadair
Lisa Cawley
Lee Hinman
Tal Levy
Gordon Brown
Colin Goodheart-Smithe