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/codegen/box/classes/kt249.kt

@@ -8,6 +8,6 @@ class Outer() {
 }
 
 fun box (): String {
-    val inner = Outer.Inner()
+    val inner = Outer.Default.Inner()
     return "OK"
 }

compiler/testData/codegen/box/enum/inclassobj.kt

@@ -1,4 +1,4 @@
-fun box() = if(Context.operatingSystemType == Context.OsType.OTHER) "OK" else "fail"
+fun box() = if(Context.operatingSystemType == Context.Default.OsType.OTHER) "OK" else "fail"
 
 public class Context
 {

compiler/testData/codegen/boxWithStdlib/whenEnumOptimization/enumInsideClassObject.kt

@@ -13,17 +13,17 @@ class A {
 
 fun foo(x : A.Default.Season) : String {
     return when (x) {
-        A.Season.WINTER -> "winter"
-        A.Season.SPRING -> "spring"
-        A.Season.SUMMER -> "summer"
+        A.Default.Season.WINTER -> "winter"
+        A.Default.Season.SPRING -> "spring"
+        A.Default.Season.SUMMER -> "summer"
         else -> "other"
     }
 }
 
 fun box() : String {
-    assertEquals("winter", foo(A.Season.WINTER))
-    assertEquals("spring", foo(A.Season.SPRING))
-    assertEquals("summer", foo(A.Season.SUMMER))
-    assertEquals("other", foo(A.Season.AUTUMN))
+    assertEquals("winter", foo(A.Default.Season.WINTER))
+    assertEquals("spring", foo(A.Default.Season.SPRING))
+    assertEquals("summer", foo(A.Default.Season.SUMMER))
+    assertEquals("other", foo(A.Default.Season.AUTUMN))
     return "OK"
 }