Add a method to reset the arguments to `std::process::Command`

std::process::Command docs

It would be cool if this struct has an option to reset all the current arguments, this would be useful fo example here:

use std::{
    io::Result,
    process::{Child, Command},
};

pub fn get_killer() -> Box<dyn FnMut(&str) -> Result<Child>> {
    let is_windows = cfg!(target_os = "windows");

    let mut cmd = Command::new(if is_windows { "cmd" } else { "pkill" });

    Box::new(move |program| {
        cmd.reset_args(); // removing previous args from previous closure calls

        if is_windows {
            cmd.args(["taskkill", "/IM", program, "/F"]);
        } else {
            cmd.arg(program);
        }

        cmd.spawn()
    })
}

Start with the linked std::process::Command documentation and the example in this issue to understand the requested argument-reset behavior. Done means reaching agreement on the API and its semantics for removing previously added arguments; no implementation files or tests are named in the payload.