Pass all available attribute information in vtkAssignAttribute

Before this change, vtkAssignAttribute::RequestInformation discarded some active attribute information instead of passing them to downstream filters.

Somewhere in my code, i use a setup like [vtkImageDta with active vectors] -> vtkAssignAttribute -> vtkImageNormalize. vtkAssignAttribute did not pass the number of components (3), so that vtkImageNormalize created the default number of components (1) in the output. This caused vtkImageNormalize to segfault, as it assumes the same number of components for the input and output scalars.