Add toStructuredText to ConstantExpression and align method names with ConstantValue

pkg/compiler/lib/src/inferrer/type_graph_dump.dart

Index: pkg/compiler/lib/src/inferrer/type_graph_dump.dart
diff --git a/pkg/compiler/lib/src/inferrer/type_graph_dump.dart b/pkg/compiler/lib/src/inferrer/type_graph_dump.dart
index a651852927e3a3bbed37300a853380fbf5890e23..3e68725b7328ecc279628aa29a6b64df05890cce 100644
--- a/pkg/compiler/lib/src/inferrer/type_graph_dump.dart
+++ b/pkg/compiler/lib/src/inferrer/type_graph_dump.dart
@@ -434,7 +434,7 @@ String formatType(TypeMask type) {
   }
   if (type is ValueTypeMask) {
     String baseType = formatType(type.forwardTo);
-    String value = type.value.toStructuredString();
+    String value = type.value.toStructuredText();
     return '$baseType=$value';
   }
   return '$type'; // Fall back on toString if not supported here.