<type_traits>: Investigate remaining issues with the _Cond_res workaround

[StephanTLavavej]

We have a workaround for DevCom-876860 / internal VSO-1049320:

STL/stl/inc/type_traits

Lines 1268 to 1294 in 969b2e2

	#if !defined(__EDG__) && !defined(__clang__) // TRANSITION, DevCom-876860
	template <class _Ty1, class _Ty2>
	using _Cond_res_if_right = // N4810 [meta.trans.other]/2.4
	decltype(false ? _Returns_exactly<_Ty1>() : _Returns_exactly<_Ty2>());
	template <class _Ty>
	using _Is_scalar_or_array = disjunction<is_scalar<_Ty>, is_array<_Ty>>;
	template <class _Ty1, class _Ty2, class = void>
	struct _Cond_res_workaround {};
	template <class _Ty1, class _Ty2>
	struct _Cond_res_workaround<_Ty1, _Ty2, void_t<_Cond_res_if_right<_Ty1, _Ty2>>> {
	using _Uty = remove_cvref_t<_Ty1>;
	using type = conditional_t<conjunction_v<is_same<_Uty, remove_cvref_t<_Ty2>>, _Is_scalar_or_array<_Uty>,
	disjunction<conjunction<is_lvalue_reference<_Ty1>, is_rvalue_reference<_Ty2>>,
	conjunction<is_rvalue_reference<_Ty1>, is_lvalue_reference<_Ty2>>>>,
	decay_t<_Copy_cv<remove_reference_t<_Ty1>, remove_reference_t<_Ty2>>>, _Cond_res_if_right<_Ty1, _Ty2>>;
	};
	template <class _Ty1, class _Ty2>
	using _Cond_res = typename _Cond_res_workaround<_Ty1, _Ty2>::type;
	#else // ^^^ workaround / no workaround vvv
	template <class _Ty1, class _Ty2>
	using _Cond_res = // N4810 [meta.trans.other]/2.4
	decltype(false ? _Returns_exactly<_Ty1>() : _Returns_exactly<_Ty2>());
	#endif // ^^^ no workaround ^^^

This was resolved as fixed by internal MSVC-PR-382810 on 2022-03-01 (which is certainly available now). However, attempting to remove this workaround still causes a test failure with VS 2022 17.3 Preview 3. We should investigate and report this problem.

The affected libcxx test is std/concepts/concepts.lang/concept.commonref/common_reference.compile.pass.cpp.

[StephanTLavavej]

@CaseyCarter has offered to take a look at this since he enjoys changing bug numbers in comments so much 🐞 😻