Add ability to sort on group work items list

What does this MR do and why?

Add ability to sort on group work items list (#393128 (closed))

Future MRs will add ability to change between open/closed/all tabs, search bar filtering, etc.

Behind feature flag namespace_level_work_items

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_2024-03-06_at_3.30.03_pm

How to set up and validate locally

1. In rails console

   Feature.enable(:namespace_level_work_items)

2. Visit any work items list page for a paid subscription group such as http://127.0.0.1:3000/groups/flightjs/-/work_items
3. Create epics
4. Confirm that you can sort the list

Related to #393128 (closed)