Add async/sync ack methods for responding to emitWithAck calls

[dontcryme]

I added asynchronous and synchronous ack functions to enable responses since there was no way to respond with ack when called via emitWithAck. Additionally, I introduced a separate ack_id variable for response handling.

 ///[sync/socket.rs]
pub(crate) struct Socket {
    //TODO: 0.4.0 refactor this
    engine_client: Arc<EngineClient>,
    connected: Arc<AtomicBool>,
    ack_id: Arc<AtomicI32>,
}
...
 pub fn ack(&self, nsp: &str, data: Payload) -> Result<()> {
        let socket_packet =
            Packet::ack_from_payload(data, nsp, Some(self.ack_id.load(Ordering::Acquire)))?;
        self.send(socket_packet)
}
...
...
 ///[async/socket.rs]
#[derive(Clone)]
pub(crate) struct Socket {
    engine_client: Arc<EngineClient>,
    connected: Arc<AtomicBool>,
    generator: StreamGenerator<Packet>,
    ack_id: Arc<AtomicI32>,
}
...
pub async fn ack(&self, nsp: &str, data: Payload) -> Result<()> {
    let socket_packet =
    Packet::ack_from_payload(data, nsp, Some(self.ack_id.load(Ordering::Acquire)))?;
    self.send(socket_packet).await
}

///[packet.rs]
pub(crate) fn ack_from_payload<'a>(
        payload: Payload,
        nsp: &'a str,
        ack_id: Option<i32>,
) ...{ ... }

The code below was tested on a Node.js Socket.IO server using emitWithAck

 ///sync use case
use rust_socketio::{ClientBuilder, Payload, RawClient};
use std::{thread::sleep, time::Duration};

fn main() {
    let callback = |payload: Payload, socket: RawClient| {
        match payload {
            #![allow(deprecated)]
            Payload::String(str) => println!("Received: {}", str),
            Payload::Binary(bin_data) => println!("Received bytes: {:#?}", bin_data),
            Payload::Text(vec) => println!("Received text: {:#?}", vec),
        }
        socket.ack("ack resend").expect("Server unreachable");
    };

    // get a socket that is connected to the admin namespace
    let socket = ClientBuilder::new("http://localhost:3000")
        //.namespace("/admin")
        .on("test", callback)
        .on("error", |err, _| eprintln!("Error: {:#?}", err))
        .connect()
        .expect("Connection failed");

    sleep(Duration::from_secs(5));
    println!("waiting...");
    socket.disconnect().expect("Disconnect failed");
    println!("disconnected waiting completed");
}

 ///async use case
use bytes::Bytes;
use futures_util::FutureExt;
use rust_socketio::{
    asynchronous::{Client, ClientBuilder},
    Payload,
};
use std::thread;
use std::time::Duration;

#[tokio::main]
async fn main() {
    let callback3 = |_payload: Payload, socket: Client| {
        async move {
            //Test React-to-Server communication (when the Socket.IO server invokes the emitWithAck method and expects a result)
            let buf: Bytes = Bytes::from_static(&[0x00, 0x01, 0x03]);
            //or socket.ack("string").await.expect("Ack invoke failed");
            socket.ack(buf).await.expect("Ack invoke failed");
        }
        .boxed()
    };

    let socket = ClientBuilder::new("http://localhost:3000")
        .namespace("/")
        .reconnect(false)
        .on("test", callback3)
        .on("error", |err, _| {
            async move { eprintln!("Error: {:#?}", err) }.boxed()
        })
        .connect()
        .await
        .expect("Connection Failed");

    thread::sleep(Duration::from_millis(25000));
    socket.disconnect().await.expect("Disconnect failed");
}

Fixes #491

[JIAQIA]

Pinging the maintainers. Could someone please review this PR? We really need this feature.