498472 project-level related work item creation

What does this MR do and why?

Updates the functionality added in !167936 (merged) so that it also works for project-level work items.

Relates to #498472 (closed) and #500998 (closed)

For non-epic work items, you should now be able to create a new related work item of the same type using the 'actions' menu in the top-right of the page.

You should also be able to select from available projects for the new work item to be created within.

References

Please include cross links to any resources that are relevant to this MR This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

MR acceptance checklist

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Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Screen_Recording_2024-11-04_at_15.35.18

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Visit an issue with work_items_view_preference feature flag enabled and ensure the work item experience is enabled.
2. Use the action menu in the top right to create a new related issue.
3. Fill in and submit the form in the modal.
4. Check the new item is appears in the linked items area of the work item you were viewing.

Doing the same as above but unchecking the 'relate to X' checkbox should create the new work item but not relate it to the original item.