Resolve "selecting numerous points, extracting, writing remote server hangs"

This has more cleanups to vtkParallelSerialWriter. Including:

• Remove unnecessary vtkTrivialProducer and ShallowCopy calls. We can now pass vtkDataObject directly to internal pipelines.
• Skip saving of empty files for nullptr or empty datasets i.e. those with no cells, points, rows, nodes etc.

Closes #16779 (closed)