Function random_string

tests/memcmp_test.cpp:30–42

using namespace sonic_json::internal::avx2;

static std::string random_string(int str_len) {
  // const char * strs =
  // "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890!@#$%^&*()这是一个字符串";
  std::string re;

  std::random_device rd;
  std::mt19937 gen(rd());
  for (int i = 0; i < str_len; ++i) {
    char c = gen() % 26 + 'a';
    re.append(1, c);
  }
  return re;
}

bool is_correct(int a, int b) {
  if (a < 0) return b < 0;