Fix N+1 queries with loading group issues with GraphQL

Merged Stan Hu requested to merge sh-fix-nplus-one-graphql-group-issues into master

Previously when group issues were queried, we called a SELECT for each project and its associated project features to check whether the user had permission to read the issue. We now solve this by preloading those items unconditionally.

I ran across this issue while trying to optimize loading of License: !50318 (merged)

Edited by Stan Hu

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