[oneDPL] [Iterators] Add a method to extract underlying iterators

[andreyfe1]

It would be great if zip_iterator has a method that extracts tuple of underlying iterators. Probably it would be useful for some other iterators as well (e.g. transform_iterator). I see that oneDPL implementation already contains it: https://github.com/oneapi-src/oneDPL/blob/main/include/oneapi/dpl/pstl/iterator_impl.h#L364

[MikeDvorskiy]

Ok. So, the issue should be closed.

[andreyfe1]

Issue is still relevant since oneDPL spec doesn't specify that method. The issue is for the Spec, not for the implementation

[akukanov]

Addressed in v1.2 specification