Update What's New Feature - Condensed Article View

What does this MR do and why?

Related to #550948 (closed), update the What's New drawer. This MR left out the read status capability from #550948 (closed), it will be implemented in a separate MR.

References

Screenshots or screen recordings

View	Main Drawer	Article View
Before
After

Screen recording (mainly to demonstrate auto fetching when items from initial fetch don't populate the drawer fully)
Screen_Recording_2025-08-07_at_2.12.31_PM

How to set up and validate locally

1. Enable whats_new_featured_carousel feature flag (gdk rails c then Feature.enable(:whats_new_featured_carousel)
2. Login to gdk or simulate SaaS: https://docs.gitlab.com/development/ee_features/#simulate-a-saas-instance
3. Go to any page, "/explore" if not logged in
4. On the bottom left, click What's new
5. Observe changes to whats new drawer

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.