Replace 'class object' with 'default object' in renderers and test data

Includes changes to decompiled text
Old syntax is used in builtins and project code for now

idea/testData/structureView/fileStructure/Render.after

@@ -12,7 +12,7 @@
   Inner1
   Inner2
  -A6
-  -class object of A6
+  -default object of A6
    test(): Unit
  -A7
   <class initializer>

idea/testData/structureView/fileStructure/Render.kt

@@ -25,7 +25,7 @@ class A5 {
     inner class Inner2
 }
 class A6 {
-    class object {
+    default object {
         fun test() {}
     }
 }