Fix work item labels widget text and dropdown size

What does this MR do and why?

Fix work item labels widget text and dropdown size (#439000 (comment 1971328973))

• Fix text to show "group" when in group context
• Fix "Create label" dropdown width to span width of button
• Fix missing injections when viewing labels widget in drawer in issues list

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

work item epic page	work item epic page	work item epic page (color widget)	issue edit page

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 epic and click on epic
4. Check that the labels widget says "Create group label" instead of "Create project label"