`<algorithm>`: `ranges::stable_sort` missing ` difference_type` casting for pointer arithmetic

[hewillk]

STL/stl/inc/algorithm

Lines 8149 to 8154 in ef62d3f

	_Uninitialized_backout<iter_value_t<_It>*> _Backout{_Temp_ptr, _Temp_ptr + _Count};
	iter_difference_t<_It> _Chunk_size = _Isort_max<_It>;
	for (;;) {
	// unconditionally merge elements back into the source buffer
	_Chunk_size <<= 1;
	_Chunked_merge_common(_Temp_ptr, _Temp_ptr + _Count, _First, _Chunk_size, _Count, _Pred, _Proj);

STL/stl/inc/algorithm

Line 8191 in ef62d3f

const auto _Backout_end = _Dest + _Count;

When _Count is an integer-class type, _Temp_ptr + _Count will be ill-formed.

#include <algorithm>
#include <ranges>
#include <vector>

int main() {
  std::vector<int> v;
  auto r = std::views::iota(0ULL, v.size())
         | std::views::transform([&v](auto i) -> auto& { return v[i]; });
  std::ranges::stable_sort(r);
}

https://godbolt.org/z/aPcq9Y6xh