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

j2k/testData/fileOrElement/staticMembers/PrivateStaticMembers.kt

@@ -5,7 +5,7 @@ class A {
         privateStatic2()
     }
 
-    class object {
+    default object {
         private val s = "abc"
 
         private fun privateStatic1() {

j2k/testData/fileOrElement/staticMembers/PrivateStaticMethods2.kt

@@ -4,7 +4,7 @@ class A {
         privateStatic2()
     }
 
-    class object {
+    default object {
 
         public fun publicStatic() {
             privateStatic1()

j2k/testData/fileOrElement/staticMembers/PrivateStaticMethods3.kt

@@ -9,7 +9,7 @@ class A {
         privateStatic2()
     }
 
-    class object {
+    default object {
 
         private fun privateStatic1() {
         }