Supported renaming default objects with default names.

idea/testData/refactoring/rename/defaultObjectWithDefaultName/after/JavaUsage.java

@@ -0,0 +1,8 @@
+class JavaUsage {
+    public static void main(String[] args) {
+        System.out.println(Foo.CONST);
+        Foo.s();
+        Foo.Baz.f();
+        Foo foo = new Foo(); // not usage of default object
+    }
+}

idea/testData/refactoring/rename/defaultObjectWithDefaultName/after/toBeRenamed.kt

@@ -0,0 +1,11 @@
+class Foo {
+    default object Baz {
+        fun f() {
+        }
+
+        platformStatic fun s() {
+        }
+
+        val CONST = 42
+    }
+}

idea/testData/refactoring/rename/defaultObjectWithDefaultName/after/usage.kt

@@ -0,0 +1,8 @@
+fun main(args: Array<String>) {
+    // class object usages
+    Foo.f()
+    val x = Foo
+
+    Foo.Baz.f()
+    val xx = Foo.Baz
+}