AttributeError: type object 'async_generator_asend' has no attribute 'f_lineno'

Bug Description

Getting AttributeError: type object 'async_generator_asend' has no attribute 'f_lineno' exceptions when handling multipart form uploads in FastAPI with uvloop.

Environment

• Python version: 3.12.11
• uvloop version: 0.21.0
• OS: Linux (Docker)
• Framework: FastAPI with uvicorn

Steps to Reproduce

1. Use FastAPI with uvloop enabled
2. Upload file via multipart form data
3. Exception appears in logs during async generator cleanup

Full Traceback

Exception ignored in: <async_generator object Request.stream at 0x7f6f1be8f920>
Traceback (most recent call last):
  File "uvloop/loop.pyx", line 3187, in uvloop.loop.Loop._asyncgen_finalizer_hook
  File "uvloop/loop.pyx", line 1289, in uvloop.loop.Loop.call_soon_threadsafe
  File "uvloop/cbhandles.pyx", line 329, in uvloop.loop.new_Handle
  File "uvloop/cbhandles.pyx", line 15, in uvloop.loop.Handle._set_loop
  File "uvloop/cbhandles.pyx", line 427, in uvloop.loop.extract_stack
  File "/usr/local/lib/python3.12/traceback.py", line 395, in extract
    return klass._extract_from_extended_frame_gen(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.12/traceback.py", line 418, in _extract_from_extended_frame_gen
    for f, (lineno, end_lineno, colno, end_colno) in frame_gen:
                                                     ^^^^^^^^^
  File "/usr/local/lib/python3.12/traceback.py", line 392, in extended_frame_gen
    for f, lineno in frame_gen:
                     ^^^^^^^^^
  File "/usr/local/lib/python3.12/traceback.py", line 336, in walk_stack
    yield f, f.f_lineno
             ^^^^^^^^^^
AttributeError: type object 'async_generator_asend' has no attribute 'f_lineno'

Linux 上で Python 3.12.11、uvloop 0.21.0、FastAPI、uvicorn を使って multipart アップロードを再現します。その後、traceback.py の呼び出しパスをコンテキストとして、uvloop/loop.pyx の _asyncgen_finalizer_hook 周辺と uvloop/cbhandles.pyx の extract_stack 周辺を調査します。非同期ジェネレーターのクリーンアップで報告された AttributeError が発生しなくなれば完了です。