Prohibit accessing nested classes/objects of class object using class literal

The fqname of class should be clear from code
Example: can't shorten A.Default.B.Default.C to A.B.C
Also fixes problem when nested class of enum class could be accessed via enum entry

compiler/testData/diagnostics/tests/classObjects/InnerClassAccessThroughEnum.kt

@@ -0,0 +1,49 @@
+package a
+
+
+enum class C {
+    E1 E2 E3 {
+        object O_O
+
+        fun b() {
+            O_O
+        }
+
+        class G
+    }
+
+    E4 {
+        fun c() {
+            //TODO: this is a bug
+            this.<!UNRESOLVED_REFERENCE!>B<!>()
+
+            C.A()
+            A()
+            //TODO: this is a bug
+            this.<!UNRESOLVED_REFERENCE!>A<!>()
+        }
+    }
+
+    class A
+    inner class B
+    object O {
+        object InO
+    }
+}
+
+fun f() {
+    C.E1.<!NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE, FUNCTION_CALL_EXPECTED!>A<!>
+    C.E1.<!NESTED_CLASS_ACCESSED_VIA_INSTANCE_REFERENCE!>A<!>()
+    C.E2.B()
+
+    C.E2.<!UNRESOLVED_REFERENCE!>O<!>
+    C.E3.<!UNRESOLVED_REFERENCE!>O<!>.<!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>InO<!>
+
+    C.O
+    C.O.InO
+    C.A()
+    C.<!UNRESOLVED_REFERENCE!>B<!>()
+
+    C.E3.<!UNRESOLVED_REFERENCE!>O_O<!>
+    C.E3.<!UNRESOLVED_REFERENCE!>G<!>()
+}