Create subclass intention implemented #KT-8473 Fixed

Can be used for implementing interfaces / abstract classes / sealed classes or extending open classes

idea/testData/quickfix/implement/enum.kt

@@ -0,0 +1,10 @@
+// "Create subclass" "false"
+// ACTION: Create test
+
+enum class <caret>My {
+    SINGLE {
+        override fun foo(): Int = 0
+    };
+
+    abstract fun foo(): Int
+}