Package splitter splits CSV files into one or more parts with round-robin
distribution. The header row is written to every output file; data rows
are assigned to outputs in order (row 0 → out1, row 1 → out2, …).
SplitCSV reads an input CSV file and distributes its rows across multiple output files
in a round-robin fashion. The header row is written to all output files.
It is equivalent to SplitCSVWithOptions(inputFilePath, outputPaths, nil).