Draft: Add MultiBlock-to-PDC conversion setting

To support moving away from Multi Block Data Sets (MBDSs) and toward Partitioned Data Set Collections (PDCs), this MR introduces a new global General Setting named AutoConvertMultiBlockDataSets. When on, any source that produces an MBDS will instead produce a PDC. When disabled (the default value), this setting does nothing and sources may still produce MBDSs.

The overall design makes use of the vtkPVPostFilter that already handles certain data conversions automatically (e.g., array component extracton, cell data to point data conversion, point data to cell data conversion). This adds a vtkConvertToPartitionedDataSetCollection filter to convert the output dataset type as well according to the global setting.

Backwards compatibility has been added that disables the conversion for state files generated by ParaView 6.2 or before. It works by adding a flag to vtkSMSourceProxy that overrides and disables the global AutoConvertMultiBlockDataSets setting for new proxies created during state loading.

TODO

• potentially override autoconversion of MBDSs if any source in the state file accepts only MBDSs. Version number may not be sufficient.
• Modify sources that only accept MBDSs to also accept PDCs to avoid production of new state files with filters that only accept MBDSs.