[Serialization] Migrate all tests to new test infrastructure

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

@@ -1,4 +1,4 @@
-// CURIOUS_ABOUT deserialize, write$Self, childSerializers, <init>, <clinit>, invoke, serializer
+// CURIOUS_ABOUT: deserialize, write$Self, childSerializers, <init>, <clinit>, invoke, serializer
 // WITH_STDLIB
 
 import kotlinx.serialization.*
@@ -16,4 +16,4 @@ sealed class Result: X {
 }
 
 @Serializable
-class Container(val r: Result)
+class Container(val r: Result)