stream模式，为啥receiver卡死的情况下，导致sender也卡死了? 一直卡在BRPC_HANDLE_EOVERCROWDED这个宏里

### 堆栈（Stack）
Stack:
#0 0x00007f7410dc6a41 clock_nanosleep@@GLIBC_2.17
#1 0x00007f7410dcbf67 __nanosleep
#2 0x00007f7410df7a49 usleep
#3 0x000000000121c897 bthread_usleep
#4 0x00000000013412e1 brpc::Stream::WriteToHostSocket(butil::IOBuf*)
#5 0x0000000001343b3a brpc::Stream::CutMessageIntoFileDescriptor(int, butil::IOBuf**, unsigned long)
#6 0x0000000001331712 brpc::Socket::StartWrite(brpc::Socket::WriteRequest*, brpc::Socket::WriteOptions const&)
#7 0x0000000001331b92 brpc::Socket::Write(butil::IOBuf*, brpc::Socket::WriteOptions const*)
#8 0x0000000001341464 brpc::Stream::AppendIfNotFull(butil::IOBuf const&)
#9 0x0000000001342ce4 brpc::StreamWrite(unsigned long, butil::IOBuf const&)
#10 0x0000000000bc87aa proxima::centaur::kafka_proxy::KafkaProxyService::send_task_job()
#11 0x00007f74110e8b74 execute_native_thread_routine
#12 0x00007f74123b73f9 start_thread
#13 0x00007f7410dffb13 __clone

### 宏定义代码

```cpp
// Sleep a while when `write_expr' returns negative with errno=EOVERCROWDED
// Implemented as a macro rather than a field of Socket.WriteOptions because
// the macro works for other functions besides Socket.Write as well.
#define BRPC_HANDLE_EOVERCROWDED(write_expr) \
({ \
int64_t __ret_code__; \
int sleep_time = 250; \
while (true) { \
__ret_code__ = (write_expr); \
if (__ret_code__ >= 0 || errno != ::brpc::EOVERCROWDED) { \
break; \
} \
sleep_time *= 2; \
if (sleep_time > 2000) { sleep_time = 2000; } \
::bthread_usleep(sleep_time); \
} \
__ret_code__; \
})
```

我看还有个BRPC_HANDLE_EOVERCROWDED_N, 想请教下当时没有用_N，是基于什么考虑呢？

Start with brpc::Stream::WriteToHostSocket, Stream::CutMessageIntoFileDescriptor, and the BRPC_HANDLE_EOVERCROWDED and BRPC_HANDLE_EOVERCROWDED_N definitions and call sites. Reproduce the stream write with a blocked receiver, compare the two macro behaviors, and determine whether the sender's prolonged sleep is expected or indicates a bug; document the conclusion with a focused regression case if needed.

Written by the indexing model from the issue text.