Please update protobuf to the latest v3.5.1 version for both ttrpc-codegen and ttrpc-compiler

[Mossaka]

Is your feature request related to a problem? Please describe.

Projects like containerd/runwasi and containerd/rust-extensions all depend on ttrpc-rust and a quick cargo build --timings shows that they are compiling protobuf twice:

Ideally, we would want to keep just one version of the protobuf, so there is this request.

Discussion

Also, I realized that ttrpc-codegen depends on ttrpc-compiler. I'd suggest to use a local path for local development and make this repo a Cargo workspace to reduce compilation time.