message: Use a single wallet batch for UpgradeKeyMetadata
diff: @@ -371,6 +371,8 @@ void CWallet::UpgradeKeyMetadata()
  return;
  }
  + std::unique_ptr<WalletBatch> batch = MakeUnique<WalletBatch>(*database);
  + size_t cnt = 0;
  for (auto& meta_pair : mapKeyMetadata) {
  CKeyMetadata& meta = meta_pair.second;
  if (!meta.hd_seed_id.IsNull() && !meta.has_key_origin && meta.hdKeypath != "s") { // If the hdKeypath is "s", that's the seed and it doesn't have a key origin
  @@ -392,10 +394,15 @@ void CWallet::UpgradeKeyMetadata()
  // Write meta to wallet
  CPubKey pubkey;
  if (GetPubKey(meta_pair.first, pubkey)) {
  - WriteKeyMetadata(meta, pubkey, true);
  + batch->WriteKeyMetadata(meta, pubkey, true);
  + if (++cnt % 1000 == 0) {
  + // avoid creating overlarge in-memory batches in case the wallet contains large amounts of keys
  + batch.reset(new WalletBatch(*database));
  }
  }
  }
  + }
  + batch.reset(); //write before setting the flag
  SetWalletFlag(WALLET_FLAG_KEY_ORIGIN_METADATA);
  }
  