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.

[webmaster128]

The next iteration of storage library storey will use MessagePack for value serialization. This ensure we don't need escaping for string and have true binary support without loosing the convenience that serde brings. MessagePack is self-describing which makes schema-less debugging possible. In #2118 we'll make add first-class support for that in the standard library.

For this reason I'll close the protobuf route here