8208611: Refactor SATBMarkQueue filtering to allow GC-specific filters

[Kim Barrett]

Please review this change to the implementation of SATB mark queue
filtering to permit a GC-specific filter to be provided.  This is a
preliminary step toward being able to share (most of) the SATB mark
queue code between G1 and Shenandoah.

We introduce a new abstract class, SATBMarkQueueFilter, which is
responsible for filtering a queue.  A SATBMarkQueueSet contains the
filter object, which is constructed and installed by the GC-specific
initialization of the qset.

The former filter function has been changed to be a function template,
with a function argument that provides the filter-out / retain
decision.  The GC-specific filter object calls that template with an
appropriate function for the GC.

For G1, it all gets nicely inlined (with gcc; I haven't looked at the
generated code for other compilers), so the only overhead for this
refactoring is the replacement of a (possibly inlined, but probably
not) ordinary function call with a virtual function call per buffer
completion.

CR:
https://bugs.openjdk.java.net/browse/JDK-8208611

Webrev:
http://cr.openjdk.java.net/~kbarrett/8208611/open.00/

Testing:
mach5 tier1-3, hs-tier4-5.