RFR: Concurrent partial should report gc+stats properly

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/concpartial-stats/webrev.01/

This fixes up the gc+stats after concurrent partial: makes sure root scans attribute to
final-partial, does a few renames.

Sample output:
 http://cr.openjdk.java.net/~shade/shenandoah/concpartial-stats/stats.txt

Testing: hotspot_gc_shenandoah, eyeballing the -Xlog:gc+stats

Thanks,
-Aleksey