Data lifecycle docs: Managing integrations data

[kilfoyle]

Integrations are the primary mechanism by which users are ingesting data, but there's only one (newly added) mention of them in the data lifecycle docs. I think we need a page to better tie together the ILM docs with the integrations content that's available in both the Fleet docs and the Integrations reference.

Let's have a page in the ILM section that includes:

• How do I find the data streams for a specific integration?
• How do I find the data stream that underlies a dashboard visualization?
• How do I find the list of all installed data streams?

And then, once I've identified the data stream that I care about, how do I go about customizing it's lifecycle policy? We have one tutorial in the ILM docs and four in the Fleet docs, so the new page should help folks to find and differentiate these.