Avoid needing the TaggedValue enum

Discussion here: https://discord.com/channels/731730685944922173/860830913390575646/1412529955841245345 where @TrueDoctor wrote:

> We would need a self describing serialization format which does store the type information but if we want arbitrary compound types to work we will always have to do some form of manual deserializaiton
>
> something like this: https://github.com/dtolnay/typetag
>
> … this crates uses a similar link time hack to generate a list of all possible implementations for deserialization as we use for our node definitions
>
> So it should be possible to remove tagged values (or we could at least experiment with that), it's just a question of if that is useful to us rn and if we should prioritize this. And I don't think we should do that since tagged values work just fine for us rn