Create a separate wrapper for work item detail sticky header

What does this MR do and why?

Iteration to clean up the work item detail. When !135530 (merged) gets merged a little more cleanup will be done which would be great 👏

Screenshots or screen recordings

No changes in before and after , for sticky header. This MR is just a refactor

How to set up and validate locally

1. In rails console enable the work_items_mvc_2 flag

   Feature.enable(:work_items_mvc_2)

2. Open any work item and scroll , you can see the sticky header in both the small and the big screens
3. Should be the same as on master

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.