Support Zach in finishing Ash.Sync

As per the threads in #electric-ash, Zach is currently stuck on:

> there are four branches of work that need to be done for it to be essentially a comprehensive FE stack on top of Ash
> improving typegen, more types, generating more useful functions,
> figuring out the pattern for partial updates, so I don't have to provide everything,
> figuring out a pattern for arbitrary mutation calling, likely this is just having a /mutate endpoint that calls actions,
> the big kahuna, which is splitting the filter into two filters, one that is supported by Electric and one that is not, and post processing the stream in some way to emit events scoped at runtime by the remaining filter.