[interpreter] Use hashmap for ConstantArrayBuilder's constant map

src/zone.h

Index: src/zone.h
diff --git a/src/zone.h b/src/zone.h
index 29055cb70d053547d44091cdfaf420e0f6736e2d..26165e9f788fdd6f0e10b05def33cb05c8c2ac32 100644
--- a/src/zone.h
+++ b/src/zone.h
@@ -158,7 +158,7 @@ class ZoneScope final {
 
 // The ZoneAllocationPolicy is used to specialize generic data
 // structures to allocate themselves and their elements in the Zone.
-class ZoneAllocationPolicy final {
+class ZoneAllocationPolicy {
  public:
   explicit ZoneAllocationPolicy(Zone* zone) : zone_(zone) { }
   void* New(size_t size) { return zone()->New(size); }