Refactor the parsing of BAML function kwargs and args by using a common library

[aaronvg]

We have a ton of places where we parse function args information:

1. Python (when we serialize things into logs)
2. Boundary studio --- when reading the logs and rendering inputs in the UI
3. VSCode --- (a) when saving and (b) rendering test contents
4. In the Rust compiler

This is currently one of the top sources of bugs, because we don't have a well defined representation of these arguments and types, and we don't have a common library with a set of utilities that can be used to render them in various places.

Current proposal is:

1. Rust package is created to serialize and deserialize any inputs/outputs related to these types
2. TS react package to provide some helper utilities on top of rust to render these objects nicely in VSCode playground, and in Boundary Studio.

[aaronvg]

We now have common utility functions in the website/common package and vscode/common package to at least read the data consistently. The urgency has dropped since we have a solution now but it'd be good to just have a common lib for all langs.