RFR(S): 8170468: Convert ParallelCompact_test to GTest

[Kirill Zhaldybin]

Dear all,

Could you please review this fix for 8170468?

The conversion was straight-forward but to get access to 
print_generic_summary_data function which was defined in cpp file 
without any class I needed to introduce a new method in 
PSParallelCompact class. Since it is private I added new friend class to 
get access to the method.
Since tested functionality is "non-product only" so are the test.

WebRev: http://cr.openjdk.java.net/~kzhaldyb/webrevs/JDK-8170468/webrev.00/

CR: https://bugs.openjdk.java.net/browse/JDK-8170468

Thank you.

Regards, Kirill