Sync ordering of epic hierarchy to work items

What does this MR do and why?

When re-ordering epics or issues within an epic we now also sync the re-ordering to the correlating work item (if one exists).

MR acceptance checklist

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Screenshots or screen recordings

Screen_Recording_2024-03-13_at_11.12.29

How to set up and validate locally

1. Feature.enable(:epic_creation_with_synced_work_item)
2. Feature.enable(:sync_epic_work_item_order)
3. Create epics & issues within a hiearchy
4. Move them around
5. Check the correlating work item (by replacing /epics/ with /work_items/ in the URL) if the hierarchy matches