[Serialization] Reorganize module structure

plugins/kotlinx-serialization/testData/codegen/Sealed.kt

@@ -0,0 +1,19 @@
+// CURIOUS_ABOUT deserialize, write$Self, childSerializers, <init>, <clinit>, invoke, serializer
+// WITH_STDLIB
+
+import kotlinx.serialization.*
+
+@Serializable
+sealed interface X {
+    fun def() {}
+}
+
+// do not forget to update this test with custom serialinfo annotation when serialization 1.3.0 is released
+@Serializable
+sealed class Result: X {
+    @Serializable class OK(val s: String): Result()
+    @Serializable object Err: Result()
+}
+
+@Serializable
+class Container(val r: Result)