[8.14] Adds a video demo to the AD docs (backport #5362)

[mergify]

Fixes #5336 by adding a video demo to the AD docs as requested by James S. The video gives an overview of how AD works and shows it in action. I added it at the top of the page. This update affects both ESS and serverless docs.

Also fixes #5361 by making a minor change to how we discuss AD's 24-hour lookback window for alerts.

Preview: ESS, Serverless

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This is an automatic backport of pull request #5362 done by Mergify.

[mergify]

Cherry-pick of ea8158c has failed:

On branch mergify/bp/8.14/pr-5362
Your branch is up to date with 'origin/8.14'.

You are currently cherry-picking commit ea8158c0.
  (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/attack-discovery/attack-discovery.asciidoc

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   docs/serverless/attack-discovery/attack-discovery.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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[benironside]

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