Deflate sampling bounds by epsilon when UseInputBounds is on

To avoid sampling outside the computed bounding box of the input data, which can happen due to floating point errors in some cases, deflate the bounding box by epsilon to ensure sampling points close to the edge of the bounds fall within the dataset. This helps when resampling vtkImageData and vtkRectilinearGrid datasets where numerical error can result in a whole planar slab of sample points falling just outside the input bounding box.