Some red squiggles are still present in `rvariant` headers & tests

[saki7]

Steps to fix:

• Fix red squiggles on VS Code + LLVM 20-21 (need @yaito3014 support)
• Fix red squiggles on Visual Studio 2026 + ReSharper (@saki7)

Also, there's some inconsistency in the current source; I think the above 4 lines can be placed inside the ReSharper macro.

iris/include/iris/rvariant/detail/variant_storage.hpp

Lines 202 to 212 in b4fe053

	variadic_union(variadic_union const&) = default;
	variadic_union(variadic_union&&) = default;
	variadic_union& operator=(variadic_union const&) = default;
	variadic_union& operator=(variadic_union&&) = default;
	#ifdef __RESHARPER__
	variadic_union(variadic_union const&) requires((!std::conjunction_v<std::is_trivially_copy_constructible<T>, std::is_trivially_copy_constructible<Ts>...>)) = delete;
	variadic_union(variadic_union&&) requires((!std::conjunction_v<std::is_trivially_move_constructible<T>, std::is_trivially_move_constructible<Ts>...>)) = delete;
	variadic_union& operator=(variadic_union const&) requires((!std::conjunction_v<std::is_trivially_copy_assignable<T>, std::is_trivially_copy_assignable<Ts>...>)) = delete;
	variadic_union& operator=(variadic_union&&) requires((!std::conjunction_v<std::is_trivially_move_assignable<T>, std::is_trivially_move_assignable<Ts>...>)) = delete;
	#endif