Doc: Add tutorial for filter-elastic_integration

[karenzone]

Starts with tutorial content from gdoc and converts it to asciidoctor format.

PREVIEW: https://logstash_bk_15932.docs-preview.app.elstc.co/guide/en/logstash/master/ea-integrations-tutorial.html

Closes: #15871

[karenzone]

run docs-build

[karenzone]

I know this is in draft form

Yes, still very much in draft form so that we can get a stake in the ground. But not too early to register directional comments, so thanks for this.

[karenzone]

@yaauie @mashhurs You requested a chance to review this "sooner rather than later." I'm still working on it, and now would be a good time to check it out. Thanks!

[jamiehynds]

Hey @karenzone, do you think this tutorial is close to being published? We're starting to promote the integrations filter to customer and internally via enablement sessions. The current documentation provides no guidance as to how to actually get the pipelines from our integrations into Logstash, and this tutorial seems to bridge that gap. If it's close to being published I can share that'll have the relevant guidance coming soon.