To validate the proposed ResultReader interface, let's update the getMore command to use this interface when building the response batch.

• In the getMore command, after retrieving the PlanExecutor from the ClientCursor, wrap the PlanExecutor in a ResultReader.
• Change the batch-filling loop to use the advance() / current() / done() interface.
• Before returning to the client, make sure the PlanExecutor is still associated with the ClientCursor.
• It may be simpler for ResultReader to hold a non-owning pointer to the PlanExecutor, rather than transferring ownership into it and back out.
• Run a correctness patch build
• Run a performance patch build