[JS IR] Add serialization regressions tests

compiler/testData/codegen/box/ir/serializationRegressions/innerClassInEnumEntryClass.kt

@@ -0,0 +1,25 @@
+// IGNORE_BACKEND_FIR: JVM_IR
+// IGNORE_BACKEND: JS_IR
+
+// MODULE: lib
+// FILE: lib.kt
+enum class A {
+    X {
+        val x = "OK"
+
+        inner class Inner {
+            val y = x
+        }
+
+        val z = Inner()
+
+        override val test: String
+            get() = z.y
+    };
+
+    abstract val test: String
+}
+
+// MODULE: main(lib)
+// FILE: main.kt
+fun box() = A.X.test