`python -m asyncio ps` fails if any task name is longer than 255 characters

Bug report

Bug description:

One task name longer than 255 characters makes python -m asyncio ps fail for the whole process. The length limit is treated as a validity check instead of a cap.

Repro:

  import asyncio
  import os
  from _remote_debugging import RemoteUnwinder

  async def main():
      asyncio.create_task(asyncio.sleep(10), name='x' * 256)
      await asyncio.sleep(0)
      print(RemoteUnwinder(os.getpid()).get_all_awaited_by())

  asyncio.run(main())

Actually:

  Traceback (most recent call last):
    File "/Users/timofeiivankov/cpython/repro.py", line 10, in <module>
      asyncio.run(main())
      ~~~~~~~~~~~^^^^^^^^
    File "/Users/timofeiivankov/cpython/Lib/asyncio/runners.py", line 205, in run
      return runner.run(main)
             ~~~~~~~~~~^^^^^^
    File "/Users/timofeiivankov/cpython/Lib/asyncio/runners.py", line 128, in run
      return self._loop.run_until_complete(task)
             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^
    File "/Users/timofeiivankov/cpython/Lib/asyncio/base_events.py", line 725, in run_until_complete
      return future.result()
             ~~~~~~~~~~~~~^^
    File "/Users/timofeiivankov/cpython/repro.py", line 8, in main
      print(RemoteUnwinder(os.getpid()).get_all_awaited_by())
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  RuntimeError: Invalid string length (256) at 0x101493800

Expected: the call returns and the long name comes back truncated:

[AwaitedInfo(thread_id=21170325, awaited_by=[
  TaskInfo(task_id=4312485712, task_name='Task-1', ...),
  TaskInfo(task_id=4312485232, task_name='xxx…' (truncated to 255), ...)])]

Proposed fix: Truncate to the limit instead of raising in object_reading.c

I have a fix ready for that

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-157790

Start in object_reading.c and reproduce the failure with the provided asyncio task-name example, using python -m asyncio ps or the shown RemoteUnwinder call. Done means the call succeeds when a task name exceeds 255 characters and the returned name is truncated to 255 characters; check linked PR gh-157790 for work already in progress.