Add rolled up dates widget in frontend

What does this MR do and why?

Add rolled up dates widget in frontend

In group level work items, add a widget for rolled up dates.

MR acceptance checklist

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

Screenshots or screen recordings

Screen Recording 2024-02-12 at 20.20.16.mov

How to set up and validate locally

1. Enable feature flags :namespace_level_work_items, :work_items_rolledup_dates
2. Visit /-/work_items on a group
3. Click create epic
4. Visit the newly created epic
5. Play around with the Inherited / Fixed dates widget.
6. You can test how inherited dates work by adding child epics or issues.

Related to #409937 (closed)