[Rust] fix: add location prefix to prevent parameter name collisions

[andershausding]

…when escaping parameter names

Fixes #21610

Generated code from test.yaml will result in this code:

pub async fn test_name_post (...) {
    // add a prefix to parameters to efficiently prevent name collisions
    let p_path_name = name;
    let p_body_body_request = body_request;
    let p_query_name = name2;
    let p_header_name = name3;
    let p_cookie_name = name4;
    (...)
}

@frol @farcaller @richardwhiuk @paladinzh @jacob-pro

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[wing328]

thanks for the PR

cc @frol (2017/07) @farcaller (2017/08) @richardwhiuk (2019/07) @paladinzh (2020/05) @jacob-pro (2022/10) @dsteeley (2025/07)