Add recovery for enum declaration without 'class' keyword

^KT-13703 Fixed

compiler/testData/psi/recovery/enumWthoutClass.kt

@@ -0,0 +1,18 @@
+enum A { X, Y }
+
+private enum B {
+    X, Y
+}
+
+internal Q {
+    X, Y
+}
+
+fun foo() {
+    // No recovery here
+    enum A { X, Y }
+
+    private enum B {
+            X, Y
+    }
+}