CSV writer doesn't include column names if metadata is not present, even if header parameter is set to true.

The CSV reader automatically generates column names if input does not have a header. Thus, current writer behavior causes the first row to be read as column names when using default parameters for both reading and writing:

  cudf_io::csv_writer_options writer_options =
    cudf_io::csv_writer_options::builder(cudf_io::sink_info{"issue.csv"}, table);
  cudf_io::write_csv(writer_options);

  cudf_io::csv_reader_options read_options =
    cudf_io::csv_reader_options::builder(udf_io::source_info{"issue.csv"});
  cudf_io::read_csv(read_options);

The APIs should work well with default parameters.

Note: this behavior is never exercised in tests because all write_csv tests use write_csv_helper, which always sets the metadata.