Include other columns in index for pending builds

What does this MR do?

Follow-up with #327142 (comment 567707927) - we extend the existing partial index to also include id, project_id information. The intent is to turn this into an index-only scan whenever possible, so we would reduce the amount of data read from the heap. This still has to check visibility, which can still be a problem.

1. Before (prod): https://explain.depesz.com/s/odKD
2. After (dblab using hypopg): https://explain.depesz.com/s/ahr8

For the query, see #327142 (closed).

Does this MR meet the acceptance criteria?

Conformity

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