message: Store seed id & path metadata in Sapling keys.
diff: @@ -40,7 +40,12 @@ libzcash::SaplingPaymentAddress SaplingScriptPubKeyMan::GenerateNewSaplingZKey()
  // Create new metadata
  int64_t nCreationTime = GetTime();
  auto ivk = xsk.expsk.full_viewing_key().in_viewing_key();
  - mapSaplingZKeyMetadata[ivk] = CKeyMetadata(nCreationTime);
  + CKeyMetadata metadata(nCreationTime);
  + metadata.key_origin.path.push_back(32 | BIP32_HARDENED_KEY_LIMIT);
  + metadata.key_origin.path.push_back(119 | BIP32_HARDENED_KEY_LIMIT);
  + metadata.key_origin.path.push_back(hdChain.nExternalChainCounter | BIP32_HARDENED_KEY_LIMIT);
  + metadata.hd_seed_id = hdChain.GetID();
  + mapSaplingZKeyMetadata[ivk] = metadata;
  auto addr = xsk.DefaultAddress();
  if (!AddSaplingZKey(xsk, addr)) {
  