Reorganize ai-powered section pages

Why is this change being made?

I noticed that the pages around Data Science section and AI-Powered stage do not match the hierarchy specified by the sections and stages YML files. In particular, there was no stage landing page, nor a directory under which all the ai-powered groups could live.

This MR addresses the problem by introducing the following changes:

• Creates a new 'ai-powered' directory under .../development/data-science/ with its proper index page as landing for the stage's information
• Moves the subdirectories for each of the stage's groups from their current location directly under ../data-science into the new ../data-science/ai-powered directory. This will provide proper breadcrumbs when looking at the group pages. This MR also updates reference links to the new location of those groups.
• It moves the content that was present in ../data-science/_index to ../data-science/ai-powered/index. The content seems more relevant to the stage than to the section. Also this MR rephrases the index at the ../data-science level to accurately represent that it is a section and list the stages.
• Add/Update references to Duo Chat in other development pages where originally only AI Framework was mentioned.

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
  • The when to get approval handbook section explains the workflow in more detail
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
  • Department: If the update affects your department, share the MR in your department Slack channel
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    • For high-priority company-wide announcements work with the internal communications team to post the update in #company-fyi and align on a plan to circulate in additional channels like the "While You Were Iterating" Newsletter

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