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/diagnostics/tests/controlFlowAnalysis/UninitializedOrReassignedVariables.kt

@@ -247,7 +247,7 @@ class ForwardAccessToBackingField() { //kt-147
 }
 
 class ClassObject() {
-    class object {
+    default object {
         val x : Int
 
         {

compiler/testData/diagnostics/tests/controlFlowAnalysis/UninitializedOrReassignedVariables.txt

@@ -49,7 +49,7 @@ package uninitialized_reassigned_variables {
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        internal class object Default {
+        internal default object Default {
             private constructor Default()
             internal final val x: kotlin.Int
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean

compiler/testData/diagnostics/tests/controlFlowAnalysis/kt1185enums.kt

@@ -10,7 +10,7 @@ enum class Direction {
 }
 
 class A {
-    class object {
+    default object {
 
     }
 }

compiler/testData/diagnostics/tests/controlFlowAnalysis/kt1185enums.txt

@@ -12,7 +12,7 @@ package kt1185 {
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        internal class object Default {
+        internal default object Default {
             private constructor Default()
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
             public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int