[Mirror] [5.1.1] 0 simd: Fix compile failures when ranges are not available

[csiefer2]

Automated mirror of upstream PR kokkos#9111 Cherry-pick of kokkos#9065 onto release-candidate-5.1.1.

Original PR: kokkos#9065

[gemini-code-assist]

Code Review

This pull request bumps the Kokkos version to 5.1.1 and updates the CHANGELOG for the 5.1.0 release. Key technical changes include the introduction of a fallback implementation for C++20 ranges within the SIMD library to support compilers with incomplete ranges support (such as Clang 14/15), the addition of a static_cast for pointer offsets in BasicView, and new unit tests for unmanaged subview construction. Feedback focuses on improving the implementation of the ranges fallback, specifically suggesting a more standard approach for concept definitions to handle Argument-Dependent Lookup and refining iterator arithmetic checks in concept requirements.

[gemini-code-assist]

The use of an immediately-invoked lambda to define a concept is highly unconventional and may lead to portability issues or confusion. A more standard approach to handle Argument-Dependent Lookup (ADL) for begin and end within a concept is to use a helper namespace.

namespace detail {
using std::begin;
using std::end;
template <class T>
concept range_impl = requires(T& t) {
  begin(t);
  end(t);
};
}
template <class R>
concept range = detail::range_impl<R>;

[gemini-code-assist]

Using an offset of 2 in the iterator arithmetic checks is arbitrary. Standard practice for verifying random access iterator properties usually involves offsets of 1 or n.

Suggested change

	{ it + 2 } -> std::same_as<Impl::iterator_t<R> >;
	{ it - 2 } -> std::same_as<Impl::iterator_t<R> >;
	{ it += 2 } -> std::same_as<Impl::iterator_t<R>&>;
	{ it -= 2 } -> std::same_as<Impl::iterator_t<R>&>;
	{ it + 1 } -> std::same_as<Impl::iterator_t<R>>;
	{ it - 1 } -> std::same_as<Impl::iterator_t<R>>;
	{ it += 1 } -> std::same_as<Impl::iterator_t<R>&>;
	{ it -= 1 } -> std::same_as<Impl::iterator_t<R>&>;