Add support for health status and iteration on work item bulk edit mutation

What does this MR do and why?

This MR adds the ability to set health status and iteration through the work items bulk edit GQL API

References

• #429994 (closed)
• #429993 (closed)

Screenshots or screen recordings

Not Provided

How to set up and validate locally

1. In an environment with the GDK running, navigate to the GraphQL explorer (http://127.0.0.1:3000/-/graphql-explorer)
2. Write a query which bulk updates multiple work items, updating the iteration and health status(es). e.g:

mutation m {
  workItemBulkUpdate(input: { ids: ["gid://gitlab/WorkItem/634", 
                                    "gid://gitlab/WorkItem/635", 
                                    "gid://gitlab/WorkItem/637",
                                    "gid://gitlab/WorkItem/8846"],
    			      parentId: "gid://gitlab/Group/33",
                              healthStatusWidget: { healthStatus: onTrack },
                              iterationWidget: { iterationId: "gid://gitlab/Iteration/6152" } }) {
    updatedWorkItemCount
    errors
  }
}

3. Observe that the health status and iteration is updated for work items supporting these widgets respectively, and ignored for those which do not support it
4. Observe that when the health status or iteration feature is disabled for a group or project, updating these is ignored

MR acceptance checklist

Evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Related to #429994 (closed)