[JS IR] Respect JsExport while assigning stable names

see https://youtrack.jetbrains.com/issue/KT-43404

js/js.translator/testData/box/jsExport/dataClass.js

@@ -0,0 +1,13 @@
+$kotlin_test_internal$.beginModule();
+
+module.exports = function() {
+    var Point = require("JS_TESTS").api.Point;
+    var p = new Point(3, 7);
+
+    return {
+        "res": p.copy(13, 11).toString()
+    };
+};
+
+$kotlin_test_internal$.endModule("lib");
+