Support KClass.nestedClasses

compiler/testData/codegen/boxWithJava/reflection/nestedClasses/J.java

@@ -0,0 +1,10 @@
+public class J {
+    public class Inner {}
+
+    public static class Nested {}
+
+    private static class PrivateNested {}
+
+    // This anonymous class should not appear in 'nestedClasses'
+    private final Object o = new Object() {};
+}