message: tests: Add fuzzing coverage for FormatHDKeypath(...) and WriteHDKeypath(...)
diff: // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  +#include <test/fuzz/FuzzedDataProvider.h>
  #include <test/fuzz/fuzz.h>
  +#include <test/fuzz/util.h>
  #include <util/bip32.h>
  +#include <cstdint>
  +#include <vector>
  +
  void test_one_input(const std::vector<uint8_t>& buffer)
  {
  const std::string keypath_str(buffer.begin(), buffer.end());
  std::vector<uint32_t> keypath;
  (void)ParseHDKeypath(keypath_str, keypath);
  +
  + FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
  + const std::vector<uint32_t> random_keypath = ConsumeRandomLengthIntegralVector<uint32_t>(fuzzed_data_provider);
  + (void)FormatHDKeypath(random_keypath);
  + (void)WriteHDKeypath(random_keypath);
  }
  