Add featured updates section

What does this MR do and why?

Add featured updates section

• Adds featured updates section to whats new drawer
• Refactor some code to separate components
• Adjust text/copies
• Adds tracking
• Feature flag to be enabled by default as per discussion in https://gitlab.com/gitlab-org/gitlab-zoekt-indexer/-/issues/88#note_2580152810

References

Screenshots or screen recordings

Before	Card 1	Card 2	Feature Flag whats_new_featured_carousel off

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
3. On the bottom left, click help
4. 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.

Related to https://gitlab.com/gitlab-org/gitlab/-/issues/550763