#7789899 Stats: Update Videos summary page

Proposed Changes

• Add a feature flag and modernise the Video summary details page
• Extend the Horizontal bar component and its card component to:
  • render additional value columns by accepting a new parameter
  • add an option for an alternate header displaying column names below the card’s title
  • update the width of the value column to accommodate larger numbers (a fixed width is needed for the label ellipsis)
  • add an option for a flexible name of the main item column (value column name is already flexible)
  • hide displaying data is loading property is passed (unlike other components, Videos summary page already have partial data when navigating to a page but still loads more)

I plan to update click events for each number in a separate PR.

Testing Instructions

• Navigate to the main Stats page on the live branch
• append ?flags=stats/new-video-summary to the URL
• visit Videos summary page by clicking View all on the component on the Traffic page
• make sure that the component loads properly
• Bonus: smoke test other horizontal bar component on different screen sizes

Before	After

Pre-merge Checklist

• Has the general commit checklist been followed? (PCYsg-hS-p2)
• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the “[Status] String Freeze” label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?
• For changes affecting Jetpack: Have we added the “[Status] Needs Privacy Updates” label if this pull request changes what data or activity we track or use (p4TIVU-ajp-p2)?

Related to #71018