JS backend: support named class objects

Temporary solution until named objects in classes are supported in js backend

js/js.translator/testData/classObject/cases/namedClassObject.kt

@@ -0,0 +1,33 @@
+package foo
+
+trait Named {
+    class object Bar {
+        val g = "a";
+    }
+}
+
+class Foo {
+    class object {
+        val g = "b";
+    }
+}
+
+fun box(): String {
+    assertEquals("a", Named.Bar.g, "Named.Bar.g")
+    assertEquals("a", Named.g, "Named.g")
+
+    assertEquals("b", Foo.Default.g, "Foo.Default.g")
+    assertEquals("b", Foo.g, "Foo.g")
+
+    assertEquals("b", foo(Foo), "foo(Foo)")
+    assertEquals("b", foo(Foo.Default), "foo(Foo.Default)")
+
+    assertEquals("c", Named.ext(), "Named.ext()")
+    assertEquals("c", Named.Bar.ext(), "Named.Bar.ext()")
+
+    return "OK"
+}
+
+fun foo(f: Foo.Default) = f.g
+
+fun Named.Bar.ext() = "c"