Reorder child records for tasks, objectives and key results
### Release notes
If you're a user of [tasks](https://docs.gitlab.com/ee/user/tasks.html#tasks) or OKRs you've likely wished more than once that we could reorder the child records within the widget! With this work, users will now be able to reorder child records within work item widgets allowing them to indicate relative priority or signal what's up next.

## Summary
Now that the child hierarchy widget is available for work items and OKR Management, we should allow users to reorder the child records within the tree with a drag and drop or similar feature.
## General availability to work item widgets
This feature should be made available for the hierarchy widgets within work items including the child hierarchy widget and the task widget.
## Dependencies
Noting that this work is related to https://gitlab.com/gitlab-org/gitlab/-/issues/385200+
## Designs
Please mimic the current experience found in Epics when dragging and dropping records in the child hierarchy widget.
##### Drag and drop example from epic's child hierarchy widget

epic