Write to trace in case class qualifier is a short reference to default object

This allows to fix some cases when there is a difference between explicit and short reference to default object
Fix shorten reference, optimize imports and import insert helper for default objects
ShortenReferences always transforms default object references to shorter form for now
Fix DescriptorUtils#getFqName() for default objects (affects test data mostly)
Fix DescriptorUtils#getImportableDescriptor()

idea/testData/refactoring/extractFunction/basic/privateMemberInClassObject.kt.conflicts

@@ -1 +1 @@
-Property A.t will become invisible after extraction
+Property A.Default.t will become invisible after extraction

idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/singletonsAndStatics/after/source/Foo.kt

@@ -3,5 +3,7 @@ package source
 import library.*
 
 class Bar {
-
+    class object {
+        val c : Int
+    }
 }

idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/singletonsAndStatics/after/target/Foo.kt

@@ -3,6 +3,7 @@ package target
 import library.JavaClass
 import library.KtClass
 import library.KtObject
+import source.Bar
 
 class Foo {
     val jv1 = JavaClass.foo()
@@ -13,4 +14,11 @@ class Foo {
     val kt2 = KtObject.foo()
     val kt3 = KtClass.Inner.foo()
     val kt4 = KtObject.Inner.foo()
+    val kt5 = KtClass.foo()
+    val kt6 = KtClass
+    val kt7 = KtClass
+
+    val kt8 = Bar
+    val kt9 = Bar
+    val kt10 = Bar.c
 }

idea/testData/refactoring/move/kotlin/moveTopLevelDeclarations/misc/singletonsAndStatics/before/source/Foo.kt

@@ -11,8 +11,17 @@ class <caret>Foo {
     val kt2 = KtObject.foo()
     val kt3 = KtClass.Inner.foo()
     val kt4 = KtObject.Inner.foo()
+    val kt5 = KtClass.Default.foo()
+    val kt6 = KtClass.Default
+    val kt7 = KtClass
+
+    val kt8 = Bar
+    val kt9 = Bar.Default
+    val kt10 = Bar.Default.c
 }
 
 class Bar {
-
+    class object {
+        val c : Int
+    }
 }