[3.14] gh-140414: add fastpath for current running loop in `asyncio.all_tasks` (GH...

[3.14] gh-140414: add fastpath for current running loop in `asyncio.all_tasks` (GH-140542) (#144494)

* gh-140414: add fastpath for current running loop in `asyncio.all_tasks` (GH-140542)

Optimize `asyncio.all_tasks()` for the common case where the event loop is running in the current thread by avoiding stop-the-world pauses and locking.

This optimization is already present for `asyncio.current_task()` so we do the same for `asyncio.all_tasks()`.
(cherry picked from commit 95e5d596308620acbd860ec25a40ef95c2b62eaa)

Co-authored-by: Kumar Aditya <kumaraditya@python.org>