Autocomplete group members in group issues search author and assignee filters

What does this MR do?

Display group and nested group and project members in the group issues search author and assignee filters

Are there points in the code the reviewer needs to double check?

• SQL performance

Why was this MR needed?

All users are displayed in the group issues search author and assignee filters. It is inconvenient.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #36702