rust: support encoding borrowed messages

[notoriaga]

needs swift-nav/dencode#2

Makes it so the encoders work with borrowed messages. Adds convenience functions to get a framed writer. Should we reexport dencode so people don't have to bring it in?

[notoriaga]

@john-michaelburke with these changes you can do something like

fn test() {
    use sbp::codec::{dencode::IterSinkExt, json::JsonEncoder, sbp::SbpEncoder};

    let input_file = std::fs::File::open("messages").unwrap();
    let log_file = std::fs::File::create("log").unwrap();
    let json_log_file = std::fs::File::create("json_log").unwrap();

    let mut bin_encoder = SbpEncoder::framed(log_file);
    let mut json_encoder = JsonEncoder::framed(json_log_file, serde_json::ser::CompactFormatter);

    for msg in iter_messages(input_file) {
        let msg = msg.unwrap();

        bin_encoder.send(&msg).unwrap();
        json_encoder.send(&msg).unwrap();
    }
}

[silverjam]

... Should we reexport dencode so people don't have to bring it in?

👍

[silverjam]

contingent on re-exporting dencode

[john-michaelburke]

Thank you for this!!