Add support for selecting namespace on the Group level

What does this MR do and why?

This MR adds support for selecting namespace on the group work items list. User will be able to select a groups and project to create any work items.

Note

Limitation: Currently, the modal is not aware of work item type being part of which namespace. For example, in the modal, a project and epic type can be created. However, it won't allow. It will be resolved with #517558 (closed).

References

• #578002 (closed)

Screenshots or screen recordings

Flow	After
Work items > New item	Screen Recording 2025-10-27 at 7.22.02 PM.mov
Global create menu > New work item	Screen Recording 2025-10-27 at 7.22.31 PM.mov

How to set up and validate locally

Prerequisite

1. Enable Consolidate list with work_item_planning_view FF

Steps to verify

1. Go to Group > Work items > New item
2. Verify you are able to create any work item in the group or subsequent projects
3. Click on the Global menu > New work item
4. Verify you are able to create any work item in the group or subsequent projects

MR acceptance checklist

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

Related to #578002 (closed)