use background_tasks.create over bare asyncio.create_task

[evnchn]

Should fix #4500

TL-DR: As in title. Should avoid GC messing up asyncio tasks since hard reference is kept.

---

Read specifically #4500 (comment) for the affected line in NiceGUI 2.13.0

Apparently, from articles in #4500 (comment), since asyncio does not itself keep a hard reference to the task created by asyncio.create_task, it can easily by GC-ed and cause Task was destroyed but it is pending!

Sitting in front of us (literally, it's 4 lines before the change in #4466), we just used background_tasks.create, which keeps a hard reference by putting all tasks into running_tasks. It has never caused trouble, or at least if it would, it should have surfaced a long long time ago (too lazy to git blame, but I bet this function introduced several versions before NiceGUI 2.13.0)

nicegui/nicegui/background_tasks.py

Lines 14 to 27 in 6ad4241

	def create(coroutine: Awaitable, *, name: str = 'unnamed task') -> asyncio.Task:
	"""Wraps a loop.create_task call and ensures there is an exception handler added to the task.
	If the task raises an exception, it is logged and handled by the global exception handlers.
	Also a reference to the task is kept until it is done, so that the task is not garbage collected mid-execution.
	See https://docs.python.org/3/library/asyncio-task.html#asyncio.create_task.
	"""
	assert core.loop is not None
	coroutine = coroutine if asyncio.iscoroutine(coroutine) else asyncio.wait_for(coroutine, None)
	task: asyncio.Task = core.loop.create_task(coroutine, name=name)
	task.add_done_callback(_handle_task_result)
	running_tasks.add(task)
	task.add_done_callback(running_tasks.discard)
	return task

[falkoschindler]

Awesome! After @chriswi93 successfully tested this PR, I think it's ready to merge. Thanks for the contribution, @evnchn! And thanks for your help, @chriswi93!