Handle high memory usage in CEMS parquet-to-duckdb conversion

[jdangerx]

Overview

Details here: #3741 (comment)

But basically, the CEMS parquet file is pretty big and that's causing a memory issue when trying to convert to DuckDB.

Success Criteria

• Hourly CEMS makes it into DuckDB

### Next steps
* [ ] figure out if we can convert the parquet file by chunks