Revisit information architecture for docs landing page and latest

We've made progress toward breaking down product siloes and offering end-to-end solutions. Our products and solutions no longer fit into neat little categories, and now represent more overlap. Ingest, for example.

Look at:
* [Docs landing page](https://www.elastic.co/guide/index.html)
* [Release docs](https://www.elastic.co/guide/en/welcome-to-elastic/current/new.html)

Revisit organizing principles?
* Support user workflows?
* Add Ingest as a category?

Immediate need: Our new Ingest docs don't fit neatly into any existing category.

Comment: Opened issue to capture raw thoughts.
ToDo: Refine and loop in @KOTungseth (and others) for discussion