Prohibit clone() for enum classes

#KT-8972 Fixed

compiler/testData/diagnostics/tests/enum/kt8972_cloneNotAllowed.kt

@@ -0,0 +1,6 @@
+enum class E : Cloneable {
+    A;
+    <!OVERRIDING_FINAL_MEMBER!>override<!> fun clone(): Any {
+        return <!AMBIGUOUS_SUPER!>super<!>.<!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>clone<!>()
+    }
+}

compiler/testData/diagnostics/tests/enum/kt8972_cloneNotAllowed.txt

@@ -0,0 +1,27 @@
+package
+
+internal final enum class E : kotlin.Enum<E>, kotlin.Cloneable {
+    public enum entry A : E {
+        private constructor A()
+        protected open override /*1*/ /*fake_override*/ fun clone(): kotlin.Any
+        public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public final override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+        public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+
+    private constructor E()
+    protected open override /*2*/ fun clone(): kotlin.Any
+    public final override /*1*/ /*fake_override*/ fun compareTo(/*0*/ other: E): kotlin.Int
+    public final override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public final override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public final override /*1*/ /*fake_override*/ fun name(): kotlin.String
+    public final override /*1*/ /*fake_override*/ fun ordinal(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+
+    // Static members
+    public final /*synthesized*/ fun valueOf(/*0*/ value: kotlin.String): E
+    public final /*synthesized*/ fun values(): kotlin.Array<E>
+}