RFR(S): Ensure collection set and cset map are consistent, and a few cleanup

[Zhengyu Gu]

Added collection set/cset fast test verification code, and restricting 
access to cset fast test map to ensure they are consistent.

Also, eliminated unused parameters in ShenandoahPolicy code, plus a few 
cleanup.

We might want to get rid of region cache in collection set. instead, 
just have collection set to wrap around cset fast test. I will 
experiment this later.

Webrev: 
http://cr.openjdk.java.net/~zgu/shenandoah/cset_cleanup/webrev.00/index.html

Thanks,

-Zhengyu