Query Wait Timout Error from Pgbouncer Not Propogating to Client

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When pgbouncer kills a connection due to its query_wait_timeout, the error message is not propagated to the client. All that is provided to the client is a not very helpful message "connection was closed in the middle of operation". This error message seems to be correctly handled by psql and psycopg.

I replicated this by using a pgbouncer instance with a pool_size of 1 and made sure another connection was consuming this connection to ensure that the connection would be put in a waiting mode.

asyncpg version
```
> python -c 'import asyncpg; print(asyncpg.__version__)'
0.31.0
```

Example asyncpg code
```python
import asyncio
import asyncpg

async def main():
conn = await asyncpg.connect('postgresql://postgres@localhost:6432/postgres')
row = await conn.execute('SELECT 1')

asyncio.run(main())
```
Stdout from the above code
```
Traceback (most recent call last):
File "", line 1, in
File "/usr/lib/python3.12/asyncio/runners.py", line 194, in run
return runner.run(main)
^^^^^^^^^^^^^^^^
File "/usr/lib/python3.12/asyncio/runners.py", line 118, in run
return self._loop.run_until_complete(task)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3.12/asyncio/base_events.py", line 687, in run_until_complete
return future.result()
^^^^^^^^^^^^^^^
File "", line 3, in main
File "/path/to/venv/lib/python3.12/site-packages/asyncpg/connection.py", line 349, in execute
result = await self._protocol.query(query, timeout)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "asyncpg/protocol/protocol.pyx", line 375, in query
asyncpg.exceptions.ConnectionDoesNotExistError: connection was closed in the middle of operation
```

Example code for psycopg
```
import psycopg
with psycopg.connect("postgresql://postgres:@localhost:6432/postgres") as conn:
with conn.cursor() as cur:
cur.execute("SELECT 1")
```

example traceback from psycopg
```
Traceback (most recent call last):
File "", line 3, in
File "/path/to/venv/lib/python3.12/site-packages/psycopg/cursor.py", line 97, in execute
raise ex.with_traceback(None)
psycopg.errors.ProtocolViolation: query_wait_timeout
```

Example call and stdout from psql on query_wait_timeout
```bash
> psql \
'postgresql://postgres:@localhost:6432/postgres' \
--command='SELECT 1'

FATAL: query_wait_timeout
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
connection to server was lost
```

Riproducete il timeout tramite la configurazione di pgbouncer descritta nell'issue, quindi iniziate dal percorso Connection.execute in asyncpg/connection.py e da query in asyncpg/protocol/protocol.pyx. Confrontate la gestione degli errori con gli esempi di psycopg e psql e verificate che il client esponga l'errore query_wait_timeout invece di segnalare soltanto una connessione chiusa.

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