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/compileJavaAgainstKotlin/platformStatic/simpleClassObjectProperty.kt

@@ -3,7 +3,7 @@ package test
 import kotlin.platform.platformStatic
 
 class A {
-    class object {
+    default object {
         [platformStatic] val b: String = "OK"
 
         var A.c: String