Allow to update requirement status widget through GraphQL

This is needed to allow changing the status of a requirement manually. To do this we should be able to run a GraphQL query that takes a parameter satisfied or failed and updates the requirement work item accordingly. It should be something like:

mutation updateWorkItem {
  workItemUpdate(input: {id: "gid://gitlab/Issue/{ISSUE_ID}", verificationStatusWidget: {status: "failed"}}) {
    workItem {
      widgets {
        ... on WorkItemWidgetVerificationStatus {
          verificationStatus
        }
      }
    }
    errors
  }
}

Important: A requirement status is delegated to its latest test report created. When doing a manual verification a new test report for the requirement with the desired status needs to be created. There is an example of how this was done before turning requirements into work items at: https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/app/services/requirements_management/update_requirement_service.rb#L28 (now removed, see b06aad0b)