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

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

@@ -0,0 +1,14 @@
+package foo
+
+open abstract class B() {
+    fun foo(arg: Int = 239 + 1): Int = arg
+}
+
+class C() : B() {
+}
+
+fun box(): String {
+    if (C().foo(10) != 10) return "fail1"
+    if (C().foo() != 240) return "fail2"
+    return "OK"
+}