AI Impact analytics - [UX] adding "Overview tiles" at the top of the page

Problem

Engineering leadership (Director/VP/CTO) need to demonstrate the ROI from the investments in AI features. To quantify the impact of adding AI and to demonstrate the ROI, they need to:

1. Analyze the effectiveness of the Code Suggestion functionality.
2. Understand the level of usage of Code Suggestion.
3. During Duo evaluation, customers need the ability to compare and report on the trial's success.

Proposal

1. Adding to the "AI Impact view" page, new overview tiles:
   1. Tile 1: GitLab Duo Pro seats: Assigned and used
   2. Tile 2: Code Suggestions: Unique Users
   3. Tile 3: Code Suggestions: Acceptance Rate %
2. Next iterations:
   1. Adding change % badge.
   2. Adding sparklines
   3. Tile 4: Duo Chat: Unique Users

Preview
⚠ This mockup may be out-of-date. For SSoT, see UX: [VSD] "AI Impact view" MVC - visualize the ... (#443698 - closed)

Tile UI copy

1. GitLab Duo Pro seats: Assigned and used
   • ℹ️ 50 out of 100 GitLab Duo assigned seats used at least one AI feature as of today.
   • See docs
2. Code Suggestions: Unique users
   • ℹ️ 23 out of 100 GitLab Duo users used Code Suggestions in the last 30 days.
   • See docs
3. Code Suggestions: Acceptance Rate
   • ℹ️ 16,245 out of 23,890 code suggestions were accepted in the last 30 days.
   • See docs
4. Duo Chat: Unique users
   • ℹ️ 50 out of 100 GitLab Duo users interacted with Duo Chat in the last 30 days.
   • See docs

Open questions

• Which time aggregation should be displayed in the tiles? last_month? month-to-date?
• ~~Can we reuse groupproduct analytics single stat as the Visualization for these tiles?~~

Data sources for the data

• Tile 1: GitLab Duo seats: Assigned and used - subscription_user_add_on_purchase_assignments
• Tile 2: Code Suggestions: Unique Users - #443696 (closed)
• Tile 3: Code Suggestions: Acceptance Rate - tbd
• Tile 4: Duo Chat: Unique users (AI Impact: collect Duo chat usage data (#459967 - closed) • Pavel Shutsin • 17.2)