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

**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](https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#local-paths-in-published-crates) and make this repo a [Cargo workspace](https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html) to reduce compilation time.