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

Nessuno ha ancora preso questa issue.

### 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:
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'
```

Riproduci il caricamento multipart con Python 3.12.11, uvloop 0.21.0, FastAPI e uvicorn su Linux. Poi esamina uvloop/loop.pyx intorno a _asyncgen_finalizer_hook e uvloop/cbhandles.pyx intorno a extract_stack, usando il percorso delle chiamate di traceback.py come contesto. Il lavoro è concluso quando la pulizia del generatore asincrono non solleva più l’AttributeError segnalato.

Scritto dal modello di indicizzazione a partire dal testo della issue.