Load Java enums as final classes

In case Java enum has an abstract member, it has the ACC_ABSTRACT flag
set in the bytecode. However, we should still load it with final
modality to be consistent with Kotlin enums which are always considered
final

 #KT-23426 Fixed

compiler/testData/compileKotlinAgainstJava/AbstractEnum.txt

@@ -2,7 +2,7 @@ package test
 
 public fun useEnum(): kotlin.String!
 
-public abstract enum class AbstractEnum : kotlin.Enum<test.AbstractEnum!> {
+public final enum class AbstractEnum : kotlin.Enum<test.AbstractEnum!> {
     enum entry ONE
 
     private constructor AbstractEnum()