Add triangle strip cell handling in vtkCurvature

vtkCurvature didn't use to handle vtkTriangleStrip cells. The Gauss curvature is computed by iterating on each triangle of triangle strip cells. The mean curvature implementation was less flexible, hence if there is at least one vtkTriangleStrip in the input, the whole input is triangulated in a local vtkPolyData prior to computing the mean curvature.

Adresses paraview/paraview#19767 (closed)