Add support for loop.sock_sendto

• uvloop version: 0.17.0 - 0.20.0
• Python version: 3.11.4 - 3.12.5
• Platform: Linux
• Can you reproduce the bug with PYTHONASYNCIODEBUG in env?: Not a bug
• Does uvloop behave differently from vanilla asyncio? How?: Yes, not implemented feature

The uvloop not implement method sock_sendto.

coroutine loop.sock_sendto(sock, data, address)
Send a datagram from sock to address. Asynchronous version of socket.sendto()

Return the number of bytes sent.
sock must be a non-blocking socket.
New in version 3.11.

The simple test case that reproduces the problem:

#!/usr/bin/env python3

import socket
import asyncio
import uvloop

uvloop.install()

async def run():
    addr = ("127.0.0.1", 1111)
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.setblocking(False)
    loop = asyncio.get_running_loop()
    await loop.sock_sendto(s, b'test', addr)

asyncio.run(run())

uvloop == 0.20.0 response:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.12/asyncio/runners.py", line 194, in run
    return runner.run(main)
           ^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.12/asyncio/runners.py", line 118, in run
    return self._loop.run_until_complete(task)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "uvloop/loop.pyx", line 1517, in uvloop.loop.Loop.run_until_complete
  File "<stdin>", line 6, in run
  File "uvloop/loop.pyx", line 2629, in sock_sendto
NotImplementedError

Start at the sock_sendto entry point in uvloop/loop.pyx, identified by the traceback, and compare its expected behavior with asyncio.loop.sock_sendto. Use the provided non-blocking UDP example to exercise the implementation. Done means the call sends the datagram and returns the number of bytes sent instead of raising NotImplementedError.