[docs] Add context to AWS integration documentation

[colleenmcginnis]

What does this PR do?

From https://github.com/elastic/observability-docs/issues/1019:

Let's audit the documentation for our top 5 integrations. The descriptions can be improved so users have a better understanding of what benefit they offer, how Elastic can help with the user's use case, and persuade them to install the integration.

This PR adds more context the AWS integration including:

• Establishes a relationship between the AWS integration/package ("AWS") and integrations for individual AWS services ("AWS CloudFront").
  • "AWS" contains detailed information about AWS credentials and permissions. "AWS CloudFront" links back to that content.
  • "AWS" contains a table with a list of all AWS services and the data associated with each. It prompts the reader to go to the pages for integrations for individual integrations to see a complete reference of all exported fields.
  • Explains why you might use "AWS" vs "AWS CloudFront" (consider using "AWS" if collecting data from 2+ services).
• Applies a new proposed structure to be applied across top integrations (overview, data types, requirements/prerequisites, setup, reference).
• Creates a soft division between guide-like content and reference-like content.
• Adds context to the "Overview":
  • Acknowledges the relationship between this integration and the larger ecosystem of Elastic products.
  • For "AWS CloudFront", provides a basic example to illustrate how this integration may be useful. (I'm not sure it's helpful for "AWS", but we could add one.)
• Adds a "Data types" section:
  • Provides a high-level overview of the kind of data that is collected. (It's difficult to derive a summary from just the reference sections since they're so long.)
  • Reinforces what "Logs" and "Metrics" are in the context of the integration.
• Adds a "Requirements" section with details about credentials/permissions (or links to "AWS" for details).
• Points the reader to the Getting started guide for step-by-step "Setup" instructions.

For the reviewer:

• I removed the "Data stream specific configuration parameters" because I think they should be addressed in each integration for individual services rather than being addressed in "AWS", but I'm open to discussing it!
• The "AWS Credentials" section definitely needs a truth-check and a close read.
• If we like the relationship between "AWS" and "AWS CloudFront" established here, we should follow up with updates to all AWS integrations.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• Review by @bmorelli25
• Review by TBD (Integrations team)

Related issues

• https://github.com/elastic/observability-docs/issues/1019

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• Start Time: 2022-06-21T19:03:42.147+0000

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[bmorelli25]

Looking good.

Side note: The md style comments <!-- Example ?? --> break the doc build. The mdx style comment is {/* this is a comment */}, which doesn't work in markdown (of course). They're fine for now, just pointing it out.

[andresrc]

ping @elastic/obs-cloud-monitoring

[kaiyan-sheng]

Hi @colleenmcginnis thanks for making the changes! Quick question, are we planning to make the same change for CloudFront to all the other integrations under AWS?

[kaiyan-sheng]

LGTM

[zmoog]

LGTM, no more nits; I love the changes you made.