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/codegen/boxWithJava/classObjectAccessor/classObject.kt

@@ -1,12 +1,12 @@
 class A {
-    class object {
+    default object {
         val i1 = 1
         val i2 = 2
     }
 }
 
 class B {
-    class object Named {
+    default object Named {
         val i1 = 3
         val i2 = 4
     }

compiler/testData/codegen/boxWithJava/platformStatic/annotations/simpleClassObject.kt

@@ -7,7 +7,7 @@ annotation class testAnnotation
 
 class A {
 
-    class object {
+    default object {
         val b: String = "OK"
 
         platformStatic testAnnotation fun test1() = b

compiler/testData/codegen/boxWithJava/platformStatic/classObject/simpleClassObject.kt

@@ -2,7 +2,7 @@ import kotlin.platform.platformStatic
 
 class A {
 
-    class object {
+    default object {
         val b: String = "OK"
 
         platformStatic val c: String = "OK"

compiler/testData/codegen/boxWithJava/properties/classObjectProperties/classObjectProperties.kt

@@ -1,17 +1,17 @@
 class Klass {
-    class object {
+    default object {
         val NAME = "Klass"
     }
 }
 
 trait Trait {
-    class object {
+    default object {
         val NAME = "Trait"
     }
 }
 
 enum class Enoom {
-    class object {
+    default object {
         val NAME = "Enoom"
     }
 }