Eng 6452 inline agg join

This is too confusing. You start with the preagg schema and resolve that to create new_output_schema which you store in m_outputSchema (maybe temporarily), then you store that same value to preagg schema, then conditionally you resolve the aggnode schema based on m_outputSchema and reset m_outputSchema to it.

Instead, start with the preagg schema and resolve that to create new_output_schema and store that back in the preagg schema. Then, conditionally set  m_outputSchema either to the aggnode schema that you resolve based on the preagg schema OR to the preagg schema directly if there is no aggnode.