FIR deserializer: support enum entries and their annotation usages

compiler/fir/resolve/testData/loadCompiledKotlin/enum/InnerEnum.txt

@@ -4,6 +4,9 @@ public final class A : R|kotlin/Any| {
     public final enum class E : R|kotlin/Enum<test/A.E>| {
         private constructor(): R|test/A.E|
 
+        public? final enum entry ENTRY {
+        }
+
     }
 
 }