sys.argv support: Consider call PySys_SetArgv on python initialization.

Currently if I use sys.argv in python code, it would complain: 'module' object has no attribute 'argv'
This is because python's argv is not initialized.

I hope PyO3 can provide an option to initialize argv in its initialization.

Repro Example

use pyo3::prelude::*;


fn main_(py: Python) -> PyResult<()> {
    let sys = py.import("sys")?;
    let argv: Vec<String> = sys.get("argv")?.extract()?;
    println!("{:?}", argv);
    Ok(())
}

fn main() -> Result<(), ()> {
    Python::with_gil(|py| {
        main_(py).map_err(|e| {
            e.print_and_set_sys_last_vars(py);
        })
    })
}

Output:

AttributeError: module 'sys' has no attribute 'argv'
Error: ()