Auto add documentation with possible type variants for Java/C#
In #670 you can notice, that with different case types in `switch-on` node resulting field type can be reduced to very generic type (for example, `Object` in Java). In order to improve user experience, we can add additional information to field documentation, that will contain all types, that field can contain. For specified example, Javadoc can be supplemented with text:
```java
/**
 * …Javadoc from `doc` attribute...
 *
 * <p>Field can have values of following classes:
 * <ul>
 * <li>{@link Inner}</li>
 * <li>{@code byte[]}</li>
 * </ul>
 */
```

Such addition do not required for languages, that can express returned type in their types. For now that will be useful at least for Java and C#