JS: move more test to box tests

js/js.translator/testData/box/trait/example.kt

@@ -0,0 +1,13 @@
+package foo
+
+interface AL {
+    fun get(index: Int): Any? = null
+}
+
+class SmartArrayList() : AL {
+}
+
+fun box(): String {
+    val c = SmartArrayList()
+    return if (null == c.get(0)) return "OK" else "fail"
+}