[JS IR] Add tests with export all file and export nested class

[JS IR] Skip dce driven for nested classes export

^KT-44469 fixed

js/js.translator/testData/box/export/exportAllFile.kt

@@ -0,0 +1,22 @@
+// IGNORE_BACKEND: JS
+// RUN_PLAIN_BOX_FUNCTION
+// INFER_MAIN_MODULE
+
+// MODULE: export-all-file
+// FILE: lib.kt
+@file:JsExport
+
+abstract class A {
+    abstract fun foo(k: String): String
+}
+
+class B : A() {
+    override fun foo(k: String): String {
+        return "O" + k
+    }
+}
+
+// FILE: test.js
+function box() {
+    return new this["export-all-file"].B().foo("K");
+}

js/js.translator/testData/box/export/exportNestedClass.kt

@@ -0,0 +1,25 @@
+// IGNORE_BACKEND: JS
+// RUN_PLAIN_BOX_FUNCTION
+// INFER_MAIN_MODULE
+// SKIP_DCE_DRIVEN
+
+// MODULE: export-nested-class
+// FILE: lib.kt
+
+abstract class A {
+    abstract fun foo(k: String): String
+}
+
+@JsExport
+class B {
+    class Foo : A() {
+        override fun foo(k: String): String {
+            return "O" + k
+        }
+    }
+}
+
+// FILE: test.js
+function box() {
+    return new this["export-nested-class"].B.Foo().foo("K");
+}