code: public final IonSystemBuilder withStreamCopyOptimized(boolean optimized)
      {
          IonSystemBuilder b = mutable();
          b.setStreamCopyOptimized(optimized);
          return b;
      }
docs: Declares whether built systems may attempt to optimize
  {@link IonWriter#writeValue(IonReader)} by copying raw source data,
  returning a new mutable builder if this is immutable.
  <p>
  <b>This feature is experimental! Please test thoroughly and report any
  issues.</b>
  
  @see #isStreamCopyOptimized()
  @see #setStreamCopyOptimized(boolean)