[JS IR] Test with js specific moved to js.translator

- Move js function from `main` to separate js file

^KT-40090 fixed

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

@@ -0,0 +1,28 @@
+// FILE: main.kt
+external class TailArgs(
+    p0: String = definedExternally,
+    p1: String = definedExternally,
+    p2: String = definedExternally,
+    p3: String = definedExternally,
+    p4: String = definedExternally,
+)
+
+external val ctorArgs: Array<String>
+
+fun box(): String {
+    val p2 = "p2"
+
+    TailArgs()
+    if (ctorArgs.size != 0) return "fail2: $ctorArgs arguments instead 0"
+
+    TailArgs(p2 = p2)
+    if (ctorArgs.size != 3 || ctorArgs[2] != p2) return "fail3: $ctorArgs arguments instead 3"
+
+    return "OK"
+}
+
+// FILE: main.js
+var ctorArgs;
+function TailArgs() {
+    ctorArgs = arguments
+}