Clean up string representations for labels

If --incompatible_descriptive_string_representations is passed, labels are converted
to strings using `repr` differently: `Label("//package:name")` instead of
`"//package:name"`

This CL doesn't affect representations of other object types but provides the
necessary infrastructure for it.

PiperOrigin-RevId: 160955284
diff --git a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java
index 256985c..b5c6a70 100644
--- a/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java
+++ b/src/test/java/com/google/devtools/build/lib/syntax/SkylarkEvaluationTest.java
@@ -55,8 +55,8 @@
    * Skylark context
    */
   @Override
-  protected ModalTestCase newTest() {
-    return new SkylarkTest();
+  protected ModalTestCase newTest(String... skylarkOptions) {
+    return new SkylarkTest(skylarkOptions);
   }
 
   @Immutable