Data lifecycle docs: Index lifecycle and phase actions

[kilfoyle]

Feedback on Index lifecycle:

• The phases descriptions are not correct. Data can still be updated in the warm and cold phases, but not in the frozen phase. You cannot ingest, but you can update (although customers do ingest on both cold and warm).

• We should include a description of each phase action on the page rather than make people follow each link, which takes them to the reference section of the docs.

• The Phase actions section is generally confusing.

  • We could add a brief description for each phase action. Or just expand the opening paragraph.

• The list of links in the Phase actions section all take me to the Reference section of the docs, and it's not obvious how to get back.

  • We could add a link from each phase action description to this Index Lifecycle page?
  • I think this is addressed nicely by [DOCS] Add signposts pointing to docs-content elasticsearch#124866 which adds a very prominent note at the top of the parent Index lifecycle actions page, differentiating the reference versus conceptual docs and linking from the former to the latter.