memory from transport buffer not freed after connection_lost

まだ誰も着手していません。

* **uvloop version**: 0.17.0
* **Python version**: 3.11.4
* **Platform**: fedora 38
* **Can you reproduce the bug with `PYTHONASYNCIODEBUG` in env?**: yes, with PYTHONASYNCIODEBUG=1
* **Does uvloop behave differently from vanilla asyncio? How?**: yes, keeps resident memory

If I flood transport.write() and then close the connection (e.g. having the client telnet session stop) the memory stays resident.
Under stock asyncio, the memory immediately is released.

To reproduce,

1. start this program,
2. watch it in top
3. , telnet to port 8888,
4. watch memory usage spike.
5. close the telnet session,
6. see that memory usage stays high.
7. repeat this experiment with stock asyncio runner,
8. the memory is freed immediately. after telnet session is closed

**This test script is a _malloc bomb_, so make sure you watch memory closely or you will consume all the memory on your machine**

```python
#!/usr/bin/env python3

import asyncio
import uvloop

class EchoServerProtocol(asyncio.Protocol):
def __init__(self, on_connect, on_disconnect):
self.on_connect = on_connect
self.on_disconnect = on_disconnect

def connection_lost(self, transport):
print('Connection lost')
self.on_disconnect()
self.transport = None

def connection_made(self, transport):
self.on_connect(transport)
peername = transport.get_extra_info('peername')
print('Connection from {}'.format(peername))
self.transport = transport

def data_received(self, data):
message = data.decode()
print('Data received: {!r}'.format(message))

print('Send: {!r}'.format(message))
self.transport.write(data)

print('Close the client socket')

async def send_data(transport):
message = b'Hello World!' * 1000
while True:
transport.write(message)
await asyncio.sleep(0)

task = None

def on_connect(transport):
global task
task = asyncio.create_task(send_data(transport))

def on_disconnect():
global task
task.cancel()

async def start():
# Get a reference to the event loop as we plan to use
# low-level APIs.
loop = asyncio.get_running_loop()

server = await loop.create_server(
lambda: EchoServerProtocol(on_connect, on_disconnect),
'127.0.0.1',
8888,
)

async with server:
await server.serve_forever()

if __name__ == '__main__':
# with asyncio.Runner() as runner:
with asyncio.Runner(loop_factory=uvloop.new_event_loop) as runner:
runner.run(start())
```

まず、提供された Python の再現コードを uvloop.new_event_loop で実行し、telnet セッションが終了した後のメモリを確認してから、標準の asyncio runner と比較します。transport buffer と connection_lost の経路を追跡します。asyncio の場合と同様に、切断後にメモリが解放されれば完了です。

索引モデルが issue の本文から書いたものです。