gh-121468: Show asyncio information in pdb

[gaogaotiantian]

This is a draft because we still need to decide on the format.

I'm aiming for something short, the original repr of asyncio task is just too long. For now it's like

gaotian@gaotian-mba cpython % ./python.exe example.py             
Task-1: <main pending>
> /Users/gaotian/programs/cpython/example.py(11)main()
-> breakpoint()

If pdb stops in an asyncio task, it will print an extra line showing the name of the task (Task-1), the name of the coroutine (main) and the status (pending).

As of now I think it will always be pending because we hit a breakpoint inside. However, we will add the feature to list all asyncio tasks in the future and allow switching between those, so we will have more status and it will be some important information.

I will work on the docs and the tests as long as the format is okay.

• Issue: Make pdb asyncio aware #121468

[Wulian233]

Line 614 has deferred import of asyncio.base_futures, so we could consider adding a lazy import of asyncio at line 606 to improve import time?

#109653
#118761

[gaogaotiantian]

asyncio will be used as long as pdb is used. pdb is not an module that is often imported explicitly or implicitly, I don't think import time of pdb is specifically critical.

[Wulian233]

You're right. I didn't realize that at the time