frontend: support serializing weights in code emission?

PR https://github.com/google/heir/pull/1501 adds support to the openfhe backend to emit dense elements in the MLIR to an external file and then load constants from there.

If we wanted support for that in the frontend, we'd need to add a shared lib for cereal when JIT-compiling. It's probably easily doable since it's an openfhe dep, but the support (and need?) for this is TBD.