AI Impact: Add GitLab Duo seats tile

Overview

As per #454953 (comment 1892918408) we want to add a tile to the top of the AI Impact dashboard with the GitLab Duo Pro seats: assigned and used information.

Proposal

1. We can reuse the component introduced in #460826 (closed)
2. Data can be retrieved as per #454953 (comment 1891455251) but we need to be mindful of permissions.
3. Tile UI - GitLab Duo seats: Assigned and used
   • ℹ️ 50 out of 100 GitLab Duo assigned seats use at least one AI feature in the last 30 days.
   • See docs
4. For the SSoT design see UX: [VSD] "AI Impact view" MVC - visualize the ... (#443698 - closed)

MVC (no historical data)	Future state (with historical data)

Next iterations

• Define pattern for handling restricted content. Consider adding the in case the user don't have permissions to view the tile data show this test on the tile "Restricted data: Your current access level does not allow viewing this information".