Require at least one filter on the root level issues query

What does this MR do and why?

Now you must provide at least one filter to the new root level issues query or you'll get an error. Related discussion in #377514 (comment 1215589429)

How to set up and validate locally

1. Enable the feature flag in Rails console Feature.enable(:root_level_issues_query)
2. Make a query like the following in order to get an error:

   {
     issues {
       nodes {
         id
       }
     }
   }

3. Make a query like the following to get results:

   {
     issues(iids: ["1"]) {
       nodes {
         id
       }
     }
   }

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 #377514 (closed)