Can't format move-only ranges

[brevzin]

Example:

#include <concepts>
#include <vector>
#include <fmt/ranges.h>

template <bool Copyable>
struct Vector {
    std::vector<int> v;

    Vector(std::initializer_list<int> elems) : v(elems) { }

    Vector(Vector&&) = default;
    Vector& operator=(Vector&&) = default;

    Vector(Vector const&) requires Copyable = default;
    Vector& operator=(Vector const&) requires Copyable = default;

    auto begin() { return v.begin(); }
    auto end() { return v.end(); }
};

static_assert(std::movable<Vector<false>>);
static_assert(std::movable<Vector<true>>);
static_assert(!std::copyable<Vector<false>>);
static_assert(std::copyable<Vector<true>>);

int main() {
    fmt::print("{}\n", Vector<true>{1, 2, 3});  // ok [1, 2, 3]
    fmt::print("{}\n", Vector<false>{1, 2, 3}); // error
}

This is because the range check for non-const ranges requires copyability and should probably just be removed (h/t @timsong-cpp):

fmt/include/fmt/ranges.h

Lines 154 to 159 in a2c05a1

	template <typename T>
	struct has_mutable_begin_end<
	T, void_t<decltype(detail::range_begin(std::declval<T>())),
	decltype(detail::range_end(std::declval<T>())),
	enable_if_t<std::is_copy_constructible<T>::value>>>
	: std::true_type {};