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/classObject/ClassObjectExplicitVisibility.kt

@@ -1,37 +1,37 @@
 package test
 
 public class PubPri {
-    private class object {}
+    private default object {}
 }
 
 public class PubInt {
-    internal class object {}
+    internal default object {}
 }
 
 public class PubPub {
-    public class object {}
+    public default object {}
 }
 
 internal class IntPri {
-    private class object {}
+    private default object {}
 }
 
 internal class IntInt {
-    internal class object {}
+    internal default object {}
 }
 
 internal class IntPub {
-    public class object {}
+    public default object {}
 }
 
 private class PriPri {
-    private class object {}
+    private default object {}
 }
 
 private class PriInt {
-    internal class object {}
+    internal default object {}
 }
 
 private class PriPub {
-    public class object {}
+    public default object {}
 }