Make parallel XML writers always available

Could we make the parallel XML writers always available? For saving traces in the GUI and then later running them in parallel it would be nice to have this. Also, through the Python API then I wouldn’t have to switch the file extension when using SaveData() whether I’m running pvbatch with a single MPI process or multiple MPI processes. It looks like it’s only removing the parallel_only="1" part in the proxy definitions but maybe I’m missing something else.

+1

FYI: Merge request at https://gitlab.kitware.com/paraview/paraview/merge_requests/3198