Add Rust convenience macros for loading

[EricLBuehler]

use mistralrs::{device, load_normal_model};
fn main() -> anyhow::Result<()> {
    let dev = Device::cuda_if_available(0)?;
    let runner = load_normal_model!(
        id = "mistralai/Mistral-7B-Instruct-v0.1".to_string(),
        kind = Mistral,
        device = dev,
        use_flash_attn = false
    );
    Ok(())
}

[github-actions]

Code Metrics Report

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 Dockerfile              1           34           25            0            9
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