Implement remaining ranges iterator concepts and modernize array

[miscco]

This implements the remaining pieces of the iterator concepts and basic ranges CPO

It cleans up the remaining <iterator> infrastructure as well as the predefined iterators reverse_iterator and move_iterator which are necessary for testing purposes later on.

Finally we also modernize <array> which is also necessary for many incoming changes as the current empty array specialization is non-conforming wrt constexpr evaluation.

Note this is currenlty based on the nonmodifying_algorithms PR as there were some merge conflicts

[gevtushenko]

suggestion: in upstream and standard these functions do not use noexcept specifier. This can have visible side effects:

struct equal_to_1 {
  template <class _T1, class _T2>
  bool operator()(const _T1& __lhs, const _T2& __rhs) const noexcept(noexcept(__lhs == __rhs)) {
    return __lhs == __rhs;
  }
};

struct equal_to_2 {
  template <class _T1, class _T2>
  bool operator()(const _T1& __lhs, const _T2& __rhs) const {
    return __lhs == __rhs;
  }
};

int main() {
  static_assert(noexcept(equal_to_1{}(1, 2)));
  static_assert(noexcept(equal_to_2{}(1, 2)));
} 

Unless there's a strong reason to deviate from upstream, I wouldn't do that (same for __less).

[miscco]

Generally, adding noexcept specifiers is allowed by the standard an QoI detial.

My point is that libc++ is not good at it and we should be better, even if we do not care about exceptions on device