Use leak-tracking recycler in InboundPipelineTests

Today we use a leaky `NON_RECYCLING_INSTANCE` in
`InboundPipelineTests#testPipelineHandling`. It's actually fine, we
don't use it for anything important, but it looks suspicious and it
means that a little bit of harmless-looking reordering would seriously
affect the coverage of these tests. This commit gets rid of it to ensure
that we're always watching for leaks.

Noticed when reviewing elastic#80656.

Author: DaveCTurner

server/src/test/java/org/elasticsearch/transport/InboundPipelineTests.java

@@ -19,7 +19,6 @@
 import org.elasticsearch.common.io.stream.RecyclerBytesStreamOutput;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.MockPageCacheRecycler;
-import org.elasticsearch.common.util.PageCacheRecycler;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
 import org.elasticsearch.core.Releasable;
 import org.elasticsearch.core.TimeValue;
@@ -93,7 +92,6 @@ public void testPipelineHandling() throws IOException {
         long totalMessages = 0;
         long bytesReceived = 0;
 
-        final BytesRefRecycler recycler = new BytesRefRecycler(PageCacheRecycler.NON_RECYCLING_INSTANCE);
         for (int i = 0; i < iterations; ++i) {
             actual.clear();
             expected.clear();
@@ -148,8 +146,9 @@ public void testPipelineHandling() throws IOException {
                     }
 
                     expected.add(new Tuple<>(messageData, expectedExceptionClass));
-                    final BytesReference reference = message.serialize(new RecyclerBytesStreamOutput(recycler));
-                    Streams.copy(reference.streamInput(), streamOutput, false);
+                    try (RecyclerBytesStreamOutput temporaryOutput = new RecyclerBytesStreamOutput(recycler)) {
+                        Streams.copy(message.serialize(temporaryOutput).streamInput(), streamOutput, false);
+                    }
                 }
 
                 final BytesReference networkBytes = streamOutput.bytes();