asyncio updates for Python 3.14

[kumaraditya303]

There have been a significant API changes in asyncio with deprecations and removals in 3.14

The following APIs are deprecated:

• asyncio.iscoroutinefunction
• asyncio.AbstractEventLoopPolicy
• asyncio.DefaultEventLoopPolicy
• asyncio.WindowsSelectorEventLoopPolicy
• asyncio.WindowsProactorEventLoopPolicy
• asyncio.get_event_loop_policy()
• asyncio.set_event_loop_policy()
• asyncio.set_event_loop()

The following APIs are removed:

• asyncio.get_child_watcher()
• asyncio.set_child_watcher()
• asyncio.AbstractEventLoopPolicy.get_child_watcher()
• asyncio.AbstractEventLoopPolicy.set_child_watcher()
• asyncio.AbstractChildWatcher
• asyncio.FastChildWatcher
• asyncio.MultiLoopChildWatcher
• asyncio.PidfdChildWatcher
• asyncio.SafeChildWatcher
• asyncio.ThreadedChildWatcher

[AlexWaygood]

Thank you! We won't start working on these until the beta period starts, per our policy (https://github.com/python/typeshed/blob/main/CONTRIBUTING.md#standard-library-stubs), but this will be a very useful reference once we get there!