Show Iteration field on items within the work items Child widget

Release notes

When viewing epic detail, planners need to be able to see which child issues are planned into which iterations (sprints) and which are not yet planned. This will allow teams to more easily make sure that all defined work is slated into sprints.

Problem to solve

It is difficult to easily see if every issue on an epic is planned into a sprint/iteration, and if so, which one they each belong to.

Additional information

Per this comment:

the child items and linked items share the common component and iteration was added for both. However, while implementing pagination on child items, we moved a few fields for optimization in the graphql which caused this issue.

This is probably an easy fix. We just need to add the iteration block in ee/work_items/graphql/work_item_metadata_widgets.fragment.graphql to view the iteration again.