`overload_compare_iterator` only supports operations required for
forward iterators. On the other hand, it is used for output iterators of
uninitialized memory algorithms, which requires it to be forward
iterator.
As a result, `overload_compare_iterator<I>::iterator_category` should
always be `std::forward_iterator_tag` if we don't extend its ability.
The correct `iterator_category` can prevent standard library
implementations like MSVC STL attempting random access operations on
`overload_compare_iterator`.
Fixes#74756.
d9c2256c97