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

idea/testData/editor/optimizeImports/DefaultObjectReference.dependency.kt

@@ -1,13 +1,13 @@
 package d
 
 class A {
-    class object E {
+    default object E {
         val c: Int
     }
 }
 
 class B {
-    class object F {
+    default object F {
         val c: Int
     }
 }

idea/testData/editor/optimizeImports/Kt2709.kt

@@ -5,7 +5,7 @@ fun main() {
 }
 
 class MyClass {
-    class object {
+    default object {
         object TEST {}
     }
 }

idea/testData/editor/optimizeImports/Kt2709.kt.after

@@ -5,7 +5,7 @@ fun main() {
 }
 
 class MyClass {
-    class object {
+    default object {
         object TEST {}
     }
 }

idea/testData/editor/optimizeImports/MembersInScope.kt

@@ -13,7 +13,7 @@ class Outer {
         inner class Inner2
     }
 
-    class object {
+    default object {
         class ClassObjectNested
     }
 

idea/testData/editor/optimizeImports/MembersInScope.kt.after

@@ -10,7 +10,7 @@ class Outer {
         inner class Inner2
     }
 
-    class object {
+    default object {
         class ClassObjectNested
     }