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/class/NamedObjectInClassObject.kt

@@ -2,7 +2,7 @@
 package test
 
 public class Outer {
-    public class object {
+    public default object {
         public object Obj {
             public val v: String = "val"
             public fun f(): String = "fun"