Add development widget to work items (feature flags)

What does this MR do and why?

MR acceptance checklist

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

How to set up and validate locally

1. Create a feature flag in a project (side menu -> Deploy -> Feature flags)
2. On the new feature flag add a linked item. This can be the url of an issue in the same project. There is no validation around what feature flag can be associated to which issue. But if you want to be able to list the feature flags in the next step, make sure the user that list the feature flags has access to the project the feature flags belong to.
3. Go to GraphiQL at http://localhost:3000/-/graphql-explorer
4. Use a query like:

   {
     project(fullPath: "flightjs/flight") {
       workItems(iid: "<iid_of_linked_issue>") {
         nodes {
           id
           widgets {
             type
             ... on WorkItemWidgetDevelopment {
               featureFlags {
                 nodes {
                   id
                   name
                   active
                 }
               }
             }
           }
         }
       }
     }
   }

Related to #452409 (closed)