Fix issue jetty#5499

this PR let the ByteAccumulator recyclable. after invoke ByteAccumulator.transferTo method
we can invoke ByteAccumulator.recycle method to reuse byte[] via ByteAccumulator.newByteArray method

Signed-off-by: Baoyi Chen <chen.bao.yi@qq.com>

jetty-websocket/websocket-common/src/main/java/org/eclipse/jetty/websocket/common/extensions/compress/ByteAccumulator.java

@@ -96,6 +96,7 @@ public void transferTo(ByteBuffer buffer)
 
     void recycle() {
         index = 0;
+        length = 0;
         prevChunks = nextChunks;
         nextChunks = new ArrayList<>();
     }