ViewerVTK: use header_type="UInt64" to use 64-bit byte counts in binary appended
This feature is mentioned under HeaderType
in these docs. Seems to have been supported for a long time.
It was not documented in the file format docs. https://vtk.org/wp-content/uploads/2015/04/file-formats.pdf (PDF was created in 2003) https://kitware.github.io/vtk-examples/site/VTKFileFormats/#xml-file-formats
I've tested with Paraview and VisIt.