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/j+k/InnerClassFromJava.kt

@@ -6,7 +6,7 @@ public interface I extends Boo {
 
 // FILE: Baz.kt
 public trait Foo {
-    class object {
+    default object {
         public val EMPTY: Foo = object : Foo{}
     }
 }

compiler/testData/diagnostics/tests/j+k/InnerClassFromJava.txt

@@ -31,7 +31,7 @@ public trait Foo {
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-    public class object Default {
+    public default object Default {
         private constructor Default()
         public final val EMPTY: Foo
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean

compiler/testData/diagnostics/tests/j+k/accessClassObjectFromJava.kt

@@ -1,5 +1,5 @@
 class Foo {
-  class object {
+  default object {
     val bar = 1
 
     fun test(<!UNUSED_PARAMETER!>a<!>: Foo.<!UNRESOLVED_REFERENCE!>`object`<!>) {

compiler/testData/diagnostics/tests/j+k/accessClassObjectFromJava.txt

@@ -6,7 +6,7 @@ internal final class Foo {
     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 bar: kotlin.Int = 1
         public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean

compiler/testData/diagnostics/tests/j+k/javaStaticImport.kt

@@ -16,7 +16,7 @@ public class AsmUtil {
 // FILE: First.kt
 package frontend
 public class JvmDeclarationOrigin {
-    class object {
+    default object {
         public val NO_ORIGIN: JvmDeclarationOrigin = JvmDeclarationOrigin()
     }
 }

compiler/testData/diagnostics/tests/j+k/javaStaticImport.txt

@@ -32,7 +32,7 @@ package frontend {
         public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
         public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
 
-        public class object Default {
+        public default object Default {
             private constructor Default()
             public final val NO_ORIGIN: frontend.JvmDeclarationOrigin
             public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean