Function convert_chunked_slice_8

fn convert_chunked_slice_8<S: Copy + Default, D: Copy>(
    src: &[S],
    dst: &mut [D],
    fn8: unsafe fn(&[S; 8]) -> [D; 8],
    fn4: unsafe fn(&[S; 4]) -> [D; 4],
)

Chunks sliced into x8 or x4 arrays