"io.grpc.StatusRuntimeException: UNKNOWN: channel closed" on network disconnect

### What version of gRPC-Java are you using?

1.44.0

### What is your environment?

Ubuntu 22.04

### What did you expect to see?

An UNAVAILABLE status code or something similar

### What did you see instead?

We saw things fail with this exception and stacktrace:
```
io.grpc.StatusRuntimeException: UNKNOWN: channel closed
at io.grpc.Status.asRuntimeException(Status.java:535)
at io.grpc.stub.ClientCalls$StreamObserverToCallListenerAdapter.onClose(ClientCalls.java:479)
at io.opentelemetry.instrumentation.grpc.v1_6.TracingClientInterceptor$TracingClientCall$TracingClientCallListener.onClose(TracingClientInterceptor.java:161)
at io.grpc.internal.ClientCallImpl.closeObserver(ClientCallImpl.java:562)
at io.grpc.internal.ClientCallImpl.access$300(ClientCallImpl.java:70)
at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInternal(ClientCallImpl.java:743)
at io.grpc.internal.ClientCallImpl$ClientStreamListenerImpl$1StreamClosed.runInContext(ClientCallImpl.java:722)
at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:133)
at com.daml.executors.QueueAwareExecutorService$TrackingRunnable.run(QueueAwareExecutorService.scala:98)
at com.daml.metrics.InstrumentedExecutorServiceMetrics$InstrumentedExecutorService$InstrumentedRunnable.run(InstrumentedExecutorServiceMetrics.scala:202)
at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1426)
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)
Caused by: java.nio.channels.ClosedChannelException: null
at io.grpc.netty.Utils.statusFromThrowable(Utils.java:271)
at io.grpc.netty.NettyClientHandler.onConnectionError(NettyClientHandler.java:500)
at io.netty.handler.codec.http2.Http2ConnectionHandler.onError(Http2ConnectionHandler.java:641)
at io.netty.handler.codec.http2.DefaultHttp2ConnectionEncoder.writeHeaders0(DefaultHttp2ConnectionEncoder.java:251)
at io.netty.handler.codec.http2.DefaultHttp2ConnectionEncoder.writeHeaders(DefaultHttp2ConnectionEncoder.java:167)
at io.netty.handler.codec.http2.DecoratingHttp2FrameWriter.writeHeaders(DecoratingHttp2FrameWriter.java:53)
at io.netty.handler.codec.http2.StreamBufferingEncoder.writeHeaders(StreamBufferingEncoder.java:170)
at io.netty.handler.codec.http2.StreamBufferingEncoder.writeHeaders(StreamBufferingEncoder.java:158)
at io.grpc.netty.NettyClientHandler.createStreamTraced(NettyClientHandler.java:609)
at io.grpc.netty.NettyClientHandler.createStream(NettyClientHandler.java:592)
at io.grpc.netty.NettyClientHandler.write(NettyClientHandler.java:326)
at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:881)
at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:863)
at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:968)
at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:856)
at io.netty.channel.DefaultChannelPipeline.write(DefaultChannelPipeline.java:1015)
at io.netty.channel.AbstractChannel.write(AbstractChannel.java:301)
at io.grpc.netty.WriteQueue$AbstractQueuedCommand.run(WriteQueue.java:213)
at io.grpc.netty.WriteQueue.flush(WriteQueue.java:128)
at io.grpc.netty.WriteQueue.access$000(WriteQueue.java:34)
at io.grpc.netty.WriteQueue$1.run(WriteQueue.java:46)
at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174)
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167)
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:566)
at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: io.netty.channel.StacklessClosedChannelException: null
at io.netty.channel.AbstractChannel$AbstractUnsafe.write(Object, ChannelPromise)(Unknown Source)
```

Interestingly, it does look like the channel recovered from this after the connection established again.

### Steps to reproduce the bug

In our test setup, we kill the connection with toxiproxy and then see this failure but only relatively rarely. I don't have a reliable reproduce unfortunately (nor one that I can make public).

Is that expected? Given that it recovers should we just retry on `UNKNOWN: channel closed` like we do on an UNAVAILABLE?

Beginne damit, io.grpc.netty.Utils.statusFromThrowable und NettyClientHandler.onConnectionError über ClientCallImpl.closeObserver hinweg nachzuverfolgen. Reproduziere die Netzwerkunterbrechung nach Möglichkeit mit dem toxiproxy-Setup und vergleiche dann den resultierenden Status mit dem erwarteten Verhalten UNAVAILABLE. Als erledigt gilt die Aufgabe, wenn das Verhalten beim Schließen des Channels verstanden und durch einen geeigneten Regressionstest abgedeckt oder als erwartungsgemäß dokumentiert ist.

Vom Indexierungsmodell aus dem Issue-Text verfasst.