Once SERVER-68970 is complete, the 'generateProjection' will, in a large number of cases, use traverseP + mkobj expressions to evaluate a projection. This method, however, is only called when translating a PROJECTION_DEFAULT.
This ticket tracks the work to extend the use of mkobj expressions when translating a PROJECTION_SIMPLE and a PROJECTION_COVERED.

(Also, this task should see whether or not this improves the performance of any workloads that leverage these query solution nodes).