At the time of writing, atlas_streams depends on the following query entities:

• 'exec_pipeline.h'
• 'LookupStage::buildPipeline'
• 'buildStage'
• AggMergeHelper
• pipeline_builder.h
• 'agg/stage.h'
• unwind_processor.h
•  src/mongo/db/exec/agg/writer_stage.h

This ticket tracks the work to remove these dependencies.