Clarify what is the default executor for `asyncio.run_in_executor`

[aisk]

Documentation

The document of asyncio said:

https://github.com/python/cpython/blob/84512c0e7f4441f060026f4fd9ddb7611fc10de4/Doc/library/asyncio-eventloop.rst?plain=1#L1263-L1264

But it dosn't mention that what is the default executor, like if it's ThreadPoolExecutor or ProcessPoolExecutor.

Someone on stackoverflow got the same question: https://stackoverflow.com/questions/60204054/default-executor-asyncio

Linked PRs

• gh-121335