gh-143341: Add callback datagram protocol

[darkdragon-001]

This avoids the need to create a child class of DatagramProtocol for many use-cases. This aligns with TCP streams which can be created via asyncio.start_server(client_connected_cb, host, port).

Usage:

async def handle_package(data, addr):
    ...

async def start_udp(host, port):
    server = await asyncio.start_datagram_endpoint(handle_package, host, port)

• Issue: Simple interface to create UDP servers #143341

[python-cla-bot]

All commit authors signed the Contributor License Agreement.

[bedevere-app]

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

[picnixz]

I'm converting it into a draft, as this requires:

• Tests.
• What's New entry & NEWS entry.
• Documentation.

[bedevere-app]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[picnixz]

Actually, I think we should first decide whether this is really useful or not as there aren't many results on GH. So, until a consensus is reached on https://discuss.python.org/c/ideas/6, I'll close the PR.