Add an option for benchmarking re-write of Ion streams via IonWriter.writeValues.

[tgregg]

IonBinaryWriterBuilder has the withStreamCopyOptimized option, which allows readers and writers to quickly transfer serialized bytes without having to materialize them. This is only exercised when the user uses IonWriter.writeValues, which this benchmark doesn't currently use. Add an option to use IonWriter.writeValues and select whether streamCopyOptimized should be enabled.