8261743: Shenandoah: enable String deduplication with compact heuristics

Reviewed-by: shade, wkemper

Author: rgithubli

src/hotspot/share/gc/shenandoah/heuristics/shenandoahCompactHeuristics.cpp

@@ -38,6 +38,7 @@ ShenandoahCompactHeuristics::ShenandoahCompactHeuristics(ShenandoahSpaceInfo* sp
   SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahImplicitGCInvokesConcurrent);
   SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahUncommit);
   SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahAlwaysClearSoftRefs);
+  SHENANDOAH_ERGO_ENABLE_FLAG(UseStringDeduplication);
   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahAllocationThreshold,  10);
   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold,   100);
   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUncommitDelay,        1000);