Show work items with epic type in issues autocomplete at project level

What does this MR do and why?

This MR enhance the capability for autocompletion in project level issues to include epics(other work items).

References

Relates to #467391 (closed)

Screenshots or screen recordings

Before	After
Screen_Recording_2025-05-08_at_2.10.15_PM	Screen_Recording_2025-05-08_at_2.07.33_PM

How to set up and validate locally

• Visit any project level issues
• Make sure you have epics to search for
• Make sure to enable namespace_level_work_items and work_item_epics flag

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.