8202722: Move marksweep_init into GC code

Reviewed-by: ehelin, kbarrett

src/hotspot/share/gc/parallel/psMarkSweep.cpp

@@ -71,6 +71,7 @@ void PSMarkSweep::initialize() {
   _span_based_discoverer.set_span(ParallelScavengeHeap::heap()->reserved_region());
   set_ref_processor(new ReferenceProcessor(&_span_based_discoverer));     // a vanilla ref proc
   _counters = new CollectorCounters("PSMarkSweep", 1);
+  MarkSweep::initialize();
 }
 
 // This method contains all heap specific policy for invoking mark sweep.