Nested classes are no more allowed inside any anonymous objects or local classes #KT-13510 Fixed

(cherry picked from commit 5c3ec6c)

compiler/testData/diagnostics/tests/objects/nestedClassInAnonymousObject.kt

@@ -0,0 +1,11 @@
+class X {
+    val foo = object {
+        <!NESTED_CLASS_NOT_ALLOWED!>class Foo<!>
+    }
+
+    fun test() {
+        object {
+            <!NESTED_CLASS_NOT_ALLOWED!>class Foo<!>
+        }
+    }
+}