[NEOS-1382] Optimize Sync based on Transformations to reduce network traffic

[nickzelei]

If a job mapping sets a GENERATE or NULL value for a specific column, we should update the input select to not include those columns.

This can potentially result in a performance increase because those columns may contain a large amount of data that can be saved by not having to go over the wire or be brought into memory.

_{From SyncLinear.com | NEOS-1382}