Align formatting of APM rules with other rules docs

[colleenmcginnis]

Description

Aligns formatting of APM rules with other rules docs. This includes:

• Splitting the current APM rules docs from one long page, to a separate page for each rule.
• Adding lists of filters, conditions, action types, and valid action variables.
• Adding an intro to APM rules in the APM section of the Observability guide with links to relevant rules docs.

So far, I've fully written the APM Anomaly rule page. If the team thinks this is a good approach, I'll finish building out the content on the pages for the rest of the APM-related rules.

Preview: https://observability-docs_bk_4366.docs-preview.app.elstc.co/guide/en/observability/master/apm-alerts.html

Documentation sets edited in this PR

Check all that apply.

• Stateful (docs/en/observability/*)
• Serverless (docs/en/serverless/*)
• Integrations Developer Guide (docs/en/integrations/*)
• None of the above

Related issue

Closes #4040

Checklist

• Product/Engineering Review
• Writer Review

Follow-up tasks

Select one.

• This PR does not need to be ported to another doc set because:
  • The concepts in this PR only apply to one doc set (serverless or stateful)
  • The PR contains edits to both doc sets (serverless and stateful)
  • Other:
    I'm not going to port to serverless right now because:
    • In the serverless docs, the APM rules are already in the alerting section.
    • There are some different options for serverless rules vs stateful rules.
    • We can align on the formatting when addressing [Request]: Improve organization and structure of docs about creating/managing rules #4128.
      Let me know if you have any concerns about this approach!
• This PR needs to be ported to another doc set:
  • Port to stateful docs: <link to PR or tracking issue>
  • Port to serverless docs: <link to PR or tracking issue>

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[colleenmcginnis]

So far, I've fully written the APM Anomaly rule page. If the team thinks this is a good approach, I'll finish building out the content on the pages for the rest of the APM-related rules.

Preview: https://observability-docs_bk_4366.docs-preview.app.elstc.co/guide/en/observability/master/apm-alerts.html

@bmorelli25 and/or @dedemorton can you take a look and let me know what you think?

[dedemorton]

In general, I think what you've done is fine. Unfortunately there are a lot of inconsistencies across the alerting topics we've developed, so suggesting the best way forward is a little tricky. (See the issue I opened about this problem.)

I'm not sure who should make the final decision about how to structure these docs (maybe Lisa?), but I think we need to establish a repeatable pattern and stick with it (in the Obs docs, in the Kibana docs, etc).

To meet the immediate objective (getting the APM rules broken out into separate topics and organized with other rules), I'm OK with you sticking to the format you have here with the understanding that we will clean this up later.

[mergify]

This pull request is now in conflict. Could you fix it @colleenmcginnis? 🙏
To fixup this pull request, you can check out it locally. See documentation: https://help.github.com/articles/checking-out-pull-requests-locally/

git fetch upstream
git checkout -b issue-4040 upstream/issue-4040
git merge upstream/main
git push upstream issue-4040

[bmorelli25]

I'm impatient and wanted to merge #4373. And that caused some conflicts with this PR. Since it was my fault, I addressed the conflicts in e43784b. Sorry !!

[bmorelli25]

Good stuff! I like where this is heading.

[bmorelli25]

🌸 ❗❗