RFR(XS) 8224679: Shenandoah: Make ShenandoahParallelCodeCacheIterator noncopyable

[Zhengyu Gu]

Copies may cause its member '_iters' to be freed multiple times.

Bug: https://bugs.openjdk.java.net/browse/JDK-8224679
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8224679/webrev.00/

Test:
   hotspot_gc_shenandoah (fastdebug and release)

Thanks,

-Zhengyu