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

compiler/testData/loadJava/compiledKotlin/annotations/classes/ClassInClassObject.kt

@@ -3,7 +3,7 @@ package test
 annotation class Anno
 
 class Class {
-    class object {
+    default object {
         Anno class Nested
     }
 }