GraphQL boards: move weight and issue count into separate queries

With GraphQL boards, it was determined that certain fields within the BoardList query were causing performance issues, specifically totalWeight and issuesCount.

Recommended first iteration approach is to just make a query call for weight and issues count separately.

On the frontend, that involves adding Apollo to boards and query at the list level for those fields.

On the backend, we need to be able to query a single BoardList (currently can only get a collection).