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

js/js.translator/testData/box/enum/implementsComparable.kt

@@ -0,0 +1,14 @@
+package foo
+
+enum class A {
+    X,
+    Y
+}
+
+fun box(): String {
+    val a : Any = A.X
+    assertEquals(0, (a as Comparable<A>).compareTo(A.X))
+    assertTrue((a as Comparable<A>).compareTo(A.Y) < 0)
+
+    return "OK"
+}