JS: create new common directory for all generated tests, migrate several tests there

js/js.translator/testData/box/defaultArguments/enumWithDefArg.kt

@@ -0,0 +1,13 @@
+package foo
+
+enum class A(val a: Int = 1) {
+    FIRST(),
+    SECOND(2)
+}
+
+fun box(): String {
+    if (A.FIRST.a == 1 && A.SECOND.a == 2) {
+        return "OK"
+    }
+    return "fail"
+}