Fix cargo protoc error

[DaviRain-Su]

Fix : #43
Relate issue: #42

• ensure ics23.rs can be regenerated via cargo protoc without breaking the build
• Enable the api.rs tests in no-std mode as well

For api.rs also passes the test under no_std is problematic, due to the use of the File and IO libraries under the standard library. However, there is no core library in core, and alloc, so now it is possible to handle it in this way and only let it test under std.

[DaviRain-Su]

@ethanfrey Hi, Can you review this PR?

[DaviRain-Su]

Relate Rust no-std: https://justjjy.com/Rust-no-std

[tzemanovic]

Thanks for updating this. I think you also need to bump prost version in rust/Cargo.toml and regenerate the proto files with the rust/codegen

[ethanfrey]

This looks better. I need to test it locally

[DaviRain-Su]

This looks better. I need to test it locally

enen, I tested it and it's OK.

[DaviRain-Su]

Thanks for updating this. I think you also need to bump prost version in rust/Cargo.toml and regenerate the proto files with the rust/codegen

Ye, I have been update cargo.toml.

[ethanfrey]

Looks good.

I checked out the code and all tests pass.

Running cargo protoc and cargo fmt will regenerate the same code.