`FlussTableITCase.testAppendWithSmallBuffer` will hang forever

When run `FlussTableITCase.testAppendWithSmallBuffer`, it's easy to fall into hang forever, and the thread stack is
```
at com.alibaba.fluss.client.write.WriterMemoryBuffer.allocate(WriterMemoryBuffer.java:187)
at com.alibaba.fluss.client.write.RecordAccumulator.allocateMemorySegment(RecordAccumulator.java:412)
at com.alibaba.fluss.client.write.RecordAccumulator.append(RecordAccumulator.java:210)
at com.alibaba.fluss.client.write.WriterClient.doSend(WriterClient.java:180)
at com.alibaba.fluss.client.write.WriterClient.send(WriterClient.java:119)
at com.alibaba.fluss.client.table.writer.TableWriter.send(TableWriter.java:71)
at com.alibaba.fluss.client.table.writer.AppendWriter.append(AppendWriter.java:64)
at com.alibaba.fluss.client.table.FlussTableITCase.testAppendWithSmallBuffer(FlussTableITCase.java:126)
```
By add `@RepeatedTest(10)` in this test, it should be reproduced

Start by running FlussTableITCase.testAppendWithSmallBuffer with @RepeatedTest(10) to reproduce the hang. Trace the path through AppendWriter.append, TableWriter.send, WriterClient.send, RecordAccumulator.append, and WriterMemoryBuffer.allocate, then verify the test completes reliably without the reported allocation wait.

Written by the indexing model from the issue text.