Function NaiveCount

cpp/src/arrow/compute/kernels/aggregate_test.cc:888–895

using CountPair = std::pair<int64_t, int64_t>;

static CountPair NaiveCount(const Array& array) {
  CountPair count;

  count.first = array.length() - array.null_count();
  count.second = array.null_count();

  return count;
}

void ValidateCount(const Array& input, CountPair expected) {
  CountOptions non_null;