This replaces SPS transparent conversion for pointers. Transparent
conversion only applies to argument/return types, not nested types. We
want to be able to serialize / deserialize structs containing pointers.
We may need to replace this in the near future with a new SPSPointer tag
type, since SPSExecutorAddr is meant to be serialization for pure
addresses, and pointers may carry other information (e.g. tag bits), but
we can do that in a follow-up commit.
Adds an overload of toSPSSerializableExpected that takes a plain T value
and returns an SPSSerializableExpected<T>. This will reduce some
boilerplate when creating SPSSerializableExpected values.
