`rust-client` marked as no_std but unconditionally depends on tonic (breaks no_std builds)

[souragc]

rust-client is marked as no_std. It uses tonic as a non optional dependency. Since tonic is not no_std, rust-client cannot be compiled for bare metal targets.

[huklaa]

I can take this. I’ll make the gRPC runtime dependencies truly optional behind the existing tonic feature, verify that the default/std feature relationships stay unchanged, and add a focused no-default-features dependency check so the bare-metal path cannot regress.

[juan518munoz]

tonic is not used by default, as the crate is pulled in with default-features = false. There's also the web-sdk compiling for the target wasm32 without the std feature.

We could argue that a true bare-metal target does not compile, but under what real scenario would we be using that architecture?