WIP: Add prost support

[ethanfrey]

We've had a lot of discussions here about how to add support for protobuf encoding in local contract storage. Forking cw-storage-plus is not that hard, but it requires that all core types in cosmwasm-std support both prost and serde encoding.

This is a demo of nicer apis to generate this alongside cw_serde as well as how to handle some patterns we have in the standard library.

It would be great to auto-generate the field tags as well to make this less work. That was demo'd in https://github.com/eira-fransham/autoproto but that code has no commit since 2021 and no tests on many lines of proc macros, so it probably requires a fork and a new maintainer before we could take that approach

[mikedotexe]

from idea to real-and-working at an unparalleled velocity
grateful.