[8.15] (Doc+) Alerts UI cannot be CCS [serverless] + bonus fixes (backport #5582)

[mergify]

Fixes included

• Serverless twin follow-up to (Doc+) Alerts UI cannot be CCS #5513
  Adds admonition about data view picker in the Alerts page.

• Updates the Data views in Elastic Security serverless page to match its ESS counterpart. It appears the serverless page was never updated to match ESS changes in Documents how to change the default security index #4695, so this gets ESS + serverless back in sync.

• Fixes URL variable/attribute usage: a few links used apm-app-ref instead of kibana-ref to point to Kibana docs. Currently the two variables have the same value, so technically the links still go to the right place, but I think that in itself is an error. We should just use the Kibana variable if we want to point to Kibana docs.

• Backports: The errant apm-app-ref attribute appears back to 8.0, but I think we can get by with fixing the current version (8.14) and moving on.

Previews

ESS:

• Data views in Elastic Security

Serverless:

• Click the link below, then in the Security card click View serverless docs.
• Navigate to: Explore your data → Data views in Elastic Security.

  ---

  This is an automatic backport of pull request (Doc+) Alerts UI cannot be CCS [serverless] + bonus fixes #5582 done by Mergify.

[mergify]

Cherry-pick of 9e7d734 has failed:

On branch mergify/bp/8.15/pr-5582
Your branch is up to date with 'origin/8.15'.

You are currently cherry-picking commit 9e7d734a.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   docs/getting-started/data-views-in-sec.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/serverless/explore/data-views-in-sec.mdx

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[github-actions]

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