RFR: 8209396: Make PtrQueueSets not statically allocated

[Kim Barrett]

Please review this change to G1BarrierSet to make its two PtrQueueSet
members (_satb_mark_queue_set and _dirty_card_queue_set) be ordinary
data members rather than static data members.

This change doesn't take advantage of the different allocation scope
to simplify construction and initialization; that's being left to some
other RFE, possibly related to JDK-8156696.

This change ties the G1BarrierSet's PtrQueueSet lifetimes to that of
the barrier set itself. Since the barrier set is never destroyed
(currently more or less intentionally), neither will the sets be
destroyed.

CR:
https://bugs.openjdk.java.net/browse/JDK-8209396

Webrev:
http://cr.openjdk.java.net/~kbarrett/8209396/open.00/

Testing:
Mach5 tier1.