Consolidate Beats guides in ingest section on elastic.co/docs

[karenzone]

We want people to start with Elastic Agent and integrations for most ingest use cases.
Currently, the eight Beats References account for half of the ingest options listed (16). The volume and visual weight send the wrong message.

Let's look at adding a single entry for Beats References, and using it to corral the Beats guides.

Wow, that's big.