Add array_chunks and array_windows?

[ronnodas]

Now that next_array exists, it's not so hard to write the methods array_chunks (functionally equivalent to from_fn(|| self.next_array())) and array_windows, similar to the unstable slice::array_chunks and slice::array_windows respectively. However it's similarly unclear what array_chunks<0> and array_windows<0> should do. Does it make sense to emit a post-monomorphization (but still compile-time) error, via say const { assert!(N > 0) }? Or is it better to produce run-time errors?

Is the name arrays preferable to array_chunks, to be consistent with Itertools::tuples?