[Serialization] Reorganize module structure

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

@@ -0,0 +1,13 @@
+// CURIOUS_ABOUT serialize, deserialize, write$Self, childSerializers, <init>, <clinit>, getDescriptor
+// WITH_STDLIB
+
+import kotlinx.serialization.*
+
+@Serializable
+class User(val firstName: String, val lastName: String)
+
+@Serializable
+class OptionalUser(val user: User = User("", ""))
+
+@Serializable
+class ListOfUsers(val list: List<User>)