add AttributeConverter to @ColumnResult

It might be a bit convenient if `@ColumnResult` could specify an `AttributeConverter`.

```java
public @interface ColumnResult {
String name();
Class type() default void.class;
Class> default AttributConverter.class;
}
```

The request concerns the Java @ColumnResult annotation and AttributeConverter type, but names no files, tests, or expected converter behavior. Start by locating the annotation declaration and related persistence API tests; done requires agreed semantics, a compatible API design, and tests demonstrating the intended conversion.

Written by the indexing model from the issue text.