[Serverless] [Attack discovery] twin PR for AI IA and AD note update

[benironside]

This is a twin PR to bring changes to serverless that are already present in ESS docs. It moves Attack discovery and AI Assistant docs into the new "AI for security" section, and also updates a note on the Attack discovery page.

Despite how many files are shown as changed (most just had their parent folder renamed), the only two that require review are:

AI for security (new section landing page)
Attack Discovery (search for "attack discovery is in". Updated that note and the following image)

[github-actions]

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[mergify]

This pull request does not have a backport label. Could you fix it @benironside? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• v7.x is the label to automatically backport to the 7.x branch.
• v7./d./d is the label to automatically backport to the 7./d branch. /d is the digit

NOTE: backport-skip has been added to this pull request.

[nastasha-solomon]

Text lgtm! I can check the HTML previews once they're up.

[elasticdocs]

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[mergify]

This pull request is now in conflicts. Could you fix it @benironside? 🙏
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 5481-serverless-AD-techprevi-update-note upstream/5481-serverless-AD-techprevi-update-note
git merge upstream/main
git push upstream 5481-serverless-AD-techprevi-update-note