message: Don't mangle list of types to string attr
  Use array of Type instead.
diff: @@ -1065,8 +1065,9 @@ StatusOr<mlir::Attribute> ImporterBase::ConvertAttributeValue(
  for (const auto& item : value.list().b())
  attrs.push_back(builder_.getBoolAttr(item));
  for (const auto& item : value.list().type()) {
  - attrs.push_back(builder_.getStringAttr(
  - mangling_util::MangleDataType(static_cast<DataType>(item))));
  + mlir::Type type;
  + TF_RETURN_IF_ERROR(ConvertDataType(DataType(item), builder_, &type));
  + attrs.push_back(mlir::TypeAttr::get(type));
  }
  for (const auto& item : value.list().shape()) {
  TF_ASSIGN_OR_RETURN(auto attr, ConvertTensorShapeProto(item));
  