[K/JS] Support companion objects in external and exported declarations

js/js.translator/testData/box/jsModule/interfacesWithCompanion.js

@@ -0,0 +1,7 @@
+define("bar", [], function() {
+    return {
+        Bar: {
+            ok() { return "OK" }
+        }
+    };
+});

js/js.translator/testData/box/jsModule/interfacesWithCompanion.kt

@@ -0,0 +1,23 @@
+// TARGET_BACKEND: JS_IR
+// TARGET_BACKEND: JS_IR_ES6
+// EXPECTED_REACHABLE_NODES: 1238
+// MODULE_KIND: AMD
+// FILE: bar.kt
+@file:JsModule("bar")
+package bar
+
+external interface Bar {
+    companion object {
+        fun ok(): String
+    }
+}
+
+// FILE: test.kt
+import bar.Bar
+
+inline fun Bar.Companion.test() = "CHECK"
+
+fun box(): String {
+    Bar.test()
+    return Bar.ok()
+}