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/InnerClassInClassObject.txt

@@ -3,7 +3,7 @@ package test
 internal final class TestFirst {
     /*primary*/ public constructor TestFirst()
 
-    internal class object Default {
+    internal default object Default {
         /*primary*/ private constructor Default()
         internal final fun testing(/*0*/ a: test.TestFirst.InnerClass): kotlin.Int
         internal final fun testing(/*0*/ a: test.TestFirst.NotInnerClass): kotlin.Int