[Serialization] Reorganize module structure

plugins/kotlinx-serialization/testData/diagnostics/IncorrectTransient.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER,-UNUSED_VARIABLE
+// WITH_STDLIB
+// SKIP_TXT
+
+import kotlinx.serialization.Serializable
+import java.io.Serializable as JavaSerializable
+
+@Serializable
+class Data(val x: Int, <!INCORRECT_TRANSIENT!>@Transient<!> val y: String)
+
+@Serializable
+class Data2(val x: Int, @Transient val y: String) : JavaSerializable