Convert a (view) index into strides and offset

[asmeurer]

It would be useful to be able to convert a view index into new set of strides and offset, so that for instance, the index could be reconstructed directly from the ndarray constructor https://numpy.org/doc/stable/reference/generated/numpy.ndarray.html (as_strided doesn't support setting an offset).

The reverse could also be useful, although more difficult as not every stride manipulation can be represented as a slice.

See also #149