GraphQL: Test for N+1 issues in additional situations in RunnerType

What does this MR do and why?

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This MR:

• improves the N+1 tests for RunnerType to also test the projects and groups properties, by adding project and group runners to the test query;
• cleans up a bit the Types::Ci::RunnerType#batched_owners method
• Requests only the id field for groups and projects, to constrain the max depth being tested.

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Part of #355740 (closed)