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/testsWithStdLib/callableReference/function/innerConstructorFromClass.kt

@@ -12,7 +12,7 @@ class A {
         y : KMemberFunction0<A, Inner>
     }
     
-    class object {
+    default object {
         fun main() {
             ::<!INACCESSIBLE_OUTER_CLASS_EXPRESSION!>Inner<!>
             val y = A::Inner

compiler/testData/diagnostics/testsWithStdLib/callableReference/function/innerConstructorFromClass.txt

@@ -7,7 +7,7 @@ internal final class A {
     internal final fun main(): kotlin.Unit
     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

compiler/testData/diagnostics/testsWithStdLib/callableReference/function/nestedConstructorFromClass.kt

@@ -12,7 +12,7 @@ class A {
         y : KFunction0<Nested>
     }
     
-    class object {
+    default object {
         fun main() {
             ::Nested
             val y = A::Nested

compiler/testData/diagnostics/testsWithStdLib/callableReference/function/nestedConstructorFromClass.txt

@@ -7,7 +7,7 @@ internal final class A {
     internal final fun main(): kotlin.Unit
     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