KT-29340 Provide effective modality for enum class in IR

* if enum class has abstract members, then it is ABSTRACT
* otherwise, if enum class has entries with members, then it is OPEN
* otherwise, it is FINAL.

compiler/testData/ir/irText/classes/enumClassModality.kt

@@ -0,0 +1,46 @@
+enum class TestFinalEnum1 {
+    X1
+}
+
+enum class TestFinalEnum2(val x: Int) {
+    X1(1)
+}
+
+enum class TestFinalEnum3 {
+    X1
+    ;
+
+    fun doStuff() {}
+}
+
+enum class TestOpenEnum1 {
+    X1 {
+        override fun toString() = "X1"
+    }
+}
+
+enum class TestOpenEnum2 {
+    X1 {
+        override fun foo() {}
+    };
+
+    open fun foo() {}
+}
+
+enum class TestAbstractEnum1 {
+    X1 {
+        override fun foo() {}
+    };
+
+    abstract fun foo()
+}
+
+interface IFoo {
+    fun foo()
+}
+
+enum class TestAbstractEnum2 : IFoo {
+    X1 {
+        override fun foo() {}
+    }
+}