[libc++] P2165R4: Update deduction guides for map containers and container adaptors

[frederick-vs-ja]

Link: https://wg21.link/P2165R4

The following alias templates needs to be defined differently since C++23.

llvm-project/libcxx/include/__iterator/iterator_traits.h

Lines 469 to 479 in b46f16c

	template <class _InputIterator>
	using __iter_key_type _LIBCPP_NODEBUG =
	__remove_const_t<typename iterator_traits<_InputIterator>::value_type::first_type>;
	template <class _InputIterator>
	using __iter_mapped_type _LIBCPP_NODEBUG = typename iterator_traits<_InputIterator>::value_type::second_type;
	template <class _InputIterator>
	using __iter_to_alloc_type _LIBCPP_NODEBUG =
	pair<const typename iterator_traits<_InputIterator>::value_type::first_type,
	typename iterator_traits<_InputIterator>::value_type::second_type>;

After changing this alias templates, it should be tested that class template argument deduction (for map, multimap, unordered_map, unordered_multimap, flat_map, and flat_multimap) actually works with tuple-like types.

[KSARK]

I've submitted a Pull Request that addresses this issue: #136011