Inconsistent handling of interfaces and enums by serializer function

Currently, `serializer<T>()` successfully lookups serializer for interfaces and implicitly serializable enums only on JVM due to reflection restriction. It also affects all reified functions such as `Json.encodeToString<T>(value)`

We have to lift this restriction in the language and provide a consistent experience across all platforms.
Also, see https://youtrack.jetbrains.com/issue/KT-41339