Display last GitLab Duo add-on activity on Duo provisioning page

Background

With the closure of #441485 (closed), we can now track GitLab Duo activity at the user level. It would be beneficial to display this data on the user provisioning page, to provide relevant information to admins on who is using Duo Pro and who is not.

Note: The GitLab Duo page has been relocated to /settings/gitlab_duo/seat_utilization as part of the Unified Duo settings work. The seat utilization page is now a child of the GitLab Duo page.

Current page

Proposal

Add a new "Last GitLab Duo activity" column to the seat utilization table while maintaining the existing "Last GitLab activity" column. This addition will provide Owners/Admins with:

• High-level insights into overall GitLab usage
• Specific visibility into GitLab Duo usage
• Ability to assess discrepancies between general platform usage and AI feature adoption

Future Considerations

• We plan to explore integration with the AI adoption dashboard in a later iteration for more comprehensive insights. Combining the "Last GitLab Duo activity" and "Last GitLab activity" columns will provide sufficient visibility for seat utilization management.
• Sorting by Last GitLab Duo activity on the Duo seat utilization page will also be explored in a later iteration