Add more feature flags to the Rust crate

[keremnymn]

Hi,

I see that the Rust crate has a lot of dependencies. For example if I want to use local connection, why am I installing all the AWS dependencies? I think more feature flags can be added for separate connection methods to reduce the dependency overhead.

[wjones127]

We can eliminate a few dependencies, but many of them are required for the breadth of functionality we offer. I created an issue to track adding some feature flags. If you have additional dependencies you think we might be able to eliminate, feel free to comment there:

#2646