IonDatagram#addAll(int, Collection) throws UnsupportedOperationException

[almann]

IonSequence declares this method as required by java.util.List:

public boolean addAll(int index, Collection<? extends IonValue> c)

However it's not currently supported for IonDatagram.

Imported from ION-83,IONJAVA-133

[raganhan]

Impl exists but needs testing

https://github.com/amzn/ion-java/blob/master/src/software/amazon/ion/impl/lite/IonDatagramLite.java#L280-L300