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

js/js.translator/testData/box/classObject/enumCompanionObject.kt

@@ -0,0 +1,15 @@
+// See KT-6326, KT-6777
+package foo
+
+enum class Foo {
+    A;
+
+    companion object {
+        val a = A
+    }
+}
+
+fun box(): String {
+    assertEquals("A", Foo.a.name)
+    return "OK"
+}