RFR: Account "shared" out-of-LAB allocations separately

[Aleksey Shipilev]

For debugging and research purposes it makes sense to record out-of-TLAB
allocations separately. Right now they are mistakenly attributed to TLAB allocs.
This change adds new counter, does a few renames, adds monitoring support
(Visualizer changes are ready), adds checks to Verifier:
   http://cr.openjdk.java.net/~shade/shenandoah/heap-account-shared/webrev.01/

Testing: hotspot_gc_shenandoah, specjvm, specjbb

Thanks,
-Aleksey