public Iterable<Map.Entry<String,Inspector>> fields() {
            var list = new ArrayList<Map.Entry<String,Inspector>>(hashlet.size());
            for (int i = 0; i < hashlet.size(); i++) {
                String fn = hashlet.key(i);
                int offset = hashlet.value(i);
                list.add(new SimpleEntry<String,Inspector>(fn, valueAt(offset)));
            }
            return list;
        }
MatchFeatureData helps pack match features for hits into
inspectable HitValue objects, all sharing the same Hashlet
for the field names.

@author arnej
vespajlib/src/main/java/com/yahoo/data/access/helpers/MatchFeatureData.java