How much can we push down into Rust?

[tantaman]

How much of the framework can we move to Rust such that we can compile a core library for use in different platforms. E.g., Swift, Kotlin.

specAndOpsToQuery is an obvious candidate.

Suggest moving up from the lowest level (specAndOps) to higher levels and see when we hit an inflection point.

The end goal being making this easy to maintain in multiple languages.