Do not depend on the implementation detail of Unpooled.buffer(int) when accessing backing array. (#8865)

Motivation:

We should not depend on the implementation detail of Unpooled.buffer(int) to allocate the exact size of backing byte[] as depending on the implementation it may return a buffer with a bigger backing array.

Modifications:

Explicit allocate the byte[] and wrap it in the ByteBuf. This way we are sure that ByteBuf.array() returns an byte[] which has the exact length and content we expect.

Result:

More correct and safe usage of ByteBuf.array()

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketServerHandshaker00.java

@@ -152,7 +152,7 @@ public class WebSocketServerHandshaker00 extends WebSocketServerHandshaker {
             int b = (int) (Long.parseLong(BEGINNING_DIGIT.matcher(key2).replaceAll("")) /
                            BEGINNING_SPACE.matcher(key2).replaceAll("").length());
             long c = req.content().readLong();
-            ByteBuf input = Unpooled.buffer(16);
+            ByteBuf input = Unpooled.wrappedBuffer(new byte[16]).setIndex(0, 0);
             input.writeInt(a);
             input.writeInt(b);
             input.writeLong(c);