vtkPolyhedron: remove per-call allocation from IsInside

vtkPolyhedron::IsInside triangulated faces with more than four vertices by constructing a vtkPolygon and a vtkIdList, then repopulating that polygon’s vtkPoints and vtkIdList for every such face. IsInside is called once per integration substep by the streamline and probe filters, so the allocation churn landed directly in the hot path, and the cached vtkPolyhedron living in vtkGenericCell’s cell store could strand those objects past leak checking.

Faces are now triangulated through vtkPolygon::EarClipPolygon3D, the shared allocation-free ear clip already used by the rendering triangulators and the polyhedron contour path, working on caller-owned scratch vectors. Results are unchanged: the solid-angle sum is independent of how a planar face is triangulated.

This compounds with the closest-point short circuit added earlier, which made EvaluatePosition call IsInside on its fast path for every substep and so raised how often the allocations were paid.