ART: Refactor GraphVisualizer attribute printing

This patch unifies the way GraphVisualizer prints instruction
attributes in preparation of changes to the Checker syntax.

Change-Id: I44e91e36c660985ddfe039a9f410fedc48b496ec
diff --git a/compiler/optimizing/ssa_liveness_analysis.h b/compiler/optimizing/ssa_liveness_analysis.h
index 82c5454..bd55e9f 100644
--- a/compiler/optimizing/ssa_liveness_analysis.h
+++ b/compiler/optimizing/ssa_liveness_analysis.h
@@ -76,7 +76,7 @@
   }
 
   void Dump(std::ostream& stream) const {
-    stream << "[" << start_ << ", " << end_ << ")";
+    stream << start_ << "-" << end_;
   }
 
   LiveRange* Dup(ArenaAllocator* allocator) const {