Drop enum class object hack

Place valueOf() and values() into the static scope of the corresponding enum
class

 #KT-5580 Fixed
 #KT-2410 Fixed

compiler/testData/compileKotlinAgainstKotlin/ClassObjectInEnum.A.kt

@@ -0,0 +1,9 @@
+package library
+
+public enum class EnumClass {
+    ENTRY
+
+    public class object {
+        public fun entry(): EnumClass = ENTRY
+    }
+}

compiler/testData/compileKotlinAgainstKotlin/ClassObjectInEnum.B.kt

@@ -0,0 +1,5 @@
+import library.EnumClass
+
+fun main(args: Array<String>) {
+    if (EnumClass.entry() != EnumClass.ENTRY) throw AssertionError()
+}