Display parent and work item ID on detail page

What does this MR do and why?

Display parent and work item ID at the top of work item detail page.

requires :use_iid_in_work_items_path feature flag.

Screenshots or screen recordings

	Before	After
Task
Objective

How to set up and validate locally

1. In rails console enable the feature flag

   Feature.enable(:use_iid_in_work_items_path)

2. Visit a work item http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/work_items/40?iid_path=true
3. Add a child to the work item using hierarchy widget
4. Visit the child
5. Ensure the parent and work item IDs are displayed at the top of the page.

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.

Related to #385308 (closed)