Provide a way to force a refresh of the cached ToOne target

When the target entity of a ToOne relationship is changed after it's resolved and cached, there is no way to force the target to refresh from the database.

Describe the solution you'd like
Provide a function that can be called that forces a new "get" from the box, caches the new entity, and returns it. This can be used when the app knows that the entity has been updated but wants those changes reflected in the related object.

Describe alternatives you've considered
As a workaround/alternative, the app can find the correct box, get an updated entity using the getTargetId(), then set the ToOne target entity to the updated entity. This works but requires a lot of extra code for something it feels like objectbox should be able to handle (especially since the ToOne relationship already knows the correct box for the get operation).

Additional context
Currently using this on Kotlin/Android.

Comienza localizando la API de relaciones ToOne y leyendo el comportamiento existente de getTargetId() y del target setter. Implementa la operación de actualización solicitada para que obtenga la entidad relacionada de su box conocida, actualice la caché y devuelva la entidad; la tarea estará terminada cuando los llamadores puedan actualizar un target modificado sin tener que encontrar la box manualmente.