Enable loading cell/point data arrays in the BaseVTKLoader

[th-skam]

This PR adds support for loading VTK cell and point data arrays as Data fields. Its creation was motivated by one recent use-case.

Two fields must be specified in the scene file:

<UnstructuredGridVTKLoader name="loader" filename="mesh.vtu"
    cellDataNames="pressure fiber_direction material_id"
    pointDataNames="temperature velocity"/>

Most of the new functions are inside the BaseVTKLoader.

• For each given name, the data arrays are loaded through loadDataArrayByName().
• The loader now manages ptrs to the newly created Data and has to delete them in doClearBuffers().
• The vtkArrayDispatch from the vtk library is used to decide the types of the data among float, double, signed/unsigned char, int, unsigned int, long, unsigned long, long long, unsigned long long. This should cover the types supported (at one point) by SOFA's native vtk loader (Int32/64/8 etc.).
• long and unsigned long are mapped to fixed-size equivalents depending on platform.
• Multi-component arrays are limited to 9 components, covering up to 3x3 tensors. Beyond that, data are rejected with a warning.

An example can be found in examples/xml/LoadDataArrays.scn and a test in TestCellPointData.cpp.

I used an AI-agent to assist with development here so some care should be taken in review.