message: Add serialization of supports expressions in features
diff: @@ -1373,6 +1373,8 @@ namespace vcpkg
  }
  serialize_paragraph(feature_obj, FeatureDeserializer::DESCRIPTION, feature->description, true);
  + serialize_optional_string(
  + feature_obj, FeatureDeserializer::SUPPORTS, to_string(feature->supports_expression));
  if (!feature->dependencies.empty() || debug)
  {
  