partitioned_by_file_group not serialized in FileScanExecConf protobuf breaks datafusion-distributed #22363

Describe the bug

The partitioned_by_file_group field in FileScanConfig is not included in the FileScanExecConf protobuf message. After deserialization, the field defaults to false, enabling work stealing? even when the original plan had it disabled.

This does seem to manifest as duplicated rows in results when using datafusion-distributed latest main.

To Reproduce

let scan_config = FileScanConfigBuilder::new(url, file_source)
    .with_partitioned_by_file_group(true)
    .build();

assert!(scan_config.partitioned_by_file_group); // true

let bytes = physical_plan_to_bytes(DataSourceExec::from_data_source(scan_config))?;
let result = physical_plan_from_bytes(bytes)?;

let config = result.downcast_ref::<DataSourceExec>()
    .data_source().downcast_ref::<FileScanConfig>();
assert!(config.partitioned_by_file_group); // FAILS - now false

Expected behavior

partitioned_by_file_group should survive protobuf roundtrip

Additional context

Field was introduced in #21351 and #21342 but not added to the protobuf schema. With 3 workers, aggregations return 3x expected values (e.g., count = 198 instead of 66).