Add filters to group.workItems query

What does this MR do and why?

Adds filters to the group.workItems GraphQL field. For now only the same filters we have at project.workItems.

How to set up and validate locally

1. Enable the feature flag in Rails console Feature.enable(:namespace_level_work_items)
2. Create multiple group level work item with the following query at http://127.0.0.1:3000/-/graphql-explorer so you can test filters in the next query

   mutation {
      workItemCreate(input: {namespacePath: "flightjs", title: "test group level work item", workItemTypeId: "gid://gitlab/WorkItems::Type/1"}) {
        errors
        workItem {
          id
        }
      }
    }

3. Use filters in the group.workItems query

   {
      group(fullPath: "flightjs") {
        name
        workItems(types: [ISSUE], state: opened) {
          nodes {
            id
            iid
            title
            widgets {
              ... on WorkItemWidgetDescription {
                type
                description
              }
            }
          }
        }
      }
    }

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #419975 (closed)