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

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

@@ -0,0 +1,16 @@
+package foo
+
+open class Base(a: Int, b: Int = 3) {
+    val c: Int
+
+    init {
+        c = a + b
+    }
+}
+
+class Derived(a: Int) : Base(a)
+
+fun box(): String {
+    assertEquals(5, Derived(2).c)
+    return "OK"
+}