message: [wallet] Add ProcessImportLegacy()
  This commit adds a ProcessImportLegacy() function which
  currently does nothing. It also unindents a block of
  code for a future move-only change.
  Reviewer hint: review with -w to ignore whitespace changes.
diff: @@ -964,6 +964,12 @@ static std::string RecurseImportData(const CScript& script, ImportData& import_d
  }
  }
  +static UniValue ProcessImportLegacy(ImportData& import_data, std::map<CKeyID, CPubKey>& pubkey_map, std::map<CKeyID, CKey>& privkey_map, std::set<CScript>& script_pub_keys, bool& have_solving_data, const UniValue& data)
  +{
  + UniValue warnings(UniValue::VARR);
  + return warnings;
  +}
  +
  static UniValue ProcessImport(CWallet * const pwallet, const UniValue& data, const int64_t timestamp) EXCLUSIVE_LOCKS_REQUIRED(pwallet->cs_wallet)
  {
  UniValue warnings(UniValue::VARR);
  @@ -983,6 +989,8 @@ static UniValue ProcessImport(CWallet * const pwallet, const UniValue& data, con
  std::set<CScript> script_pub_keys;
  bool have_solving_data;
  + warnings = ProcessImportLegacy(import_data, pubkey_map, privkey_map, script_pub_keys, have_solving_data, data);
  +
  // First ensure scriptPubKey has either a script or JSON with "address" string
  const UniValue& scriptPubKey = data["scriptPubKey"];
  bool isScript = scriptPubKey.getType() == UniValue::VSTR;
  