Play Framework

[PF-31] Netty 3.10 -> Netty 4.2 Stage A: dep swap + non-WebSocket HTTP path

Replaces the bundled netty-3.10.6.Final.jar with the modular Netty 4.2.12
artifacts (buffer, codec-base, codec-http, common, handler, resolver,
transport) and migrates the server-side glue to the Netty 4 API. WebSocket
support and large-body disk-spooling are intentionally stubbed in this
stage; PF-32 (Stage B) restores StreamChunkAggregator-style spooling and
PF-33 (Stage C) restores the full WebSocket handshake + frame handling.

Codec/transport migration:
- Server.java: ServerBootstrap now uses bossGroup/workerGroup
  EventLoopGroups + NioServerSocketChannel.class (replaced the Netty 3
  NioServerSocketChannelFactory + Executors pair). bind() now
  syncUninterruptibly() so startup failures are surfaced.
  childOption(TCP_NODELAY) replaces setOption("child.tcpNoDelay").
- HttpServerPipelineFactory / SslHttpServerPipelineFactory: now extend
  ChannelInitializer<Channel> instead of implementing ChannelPipelineFactory.
  Default pipeline switches play.server.StreamChunkAggregator for the stock
  io.netty.handler.codec.http.HttpObjectAggregator (1 MB cap configurable
  via play.netty.maxContentLength). Reflective handler construction
  special-cases HttpObjectAggregator's int-arg ctor.
- PlayHandler: extends ChannelInboundHandlerAdapter (was
  SimpleChannelUpstreamHandler). messageReceived(ctx, MessageEvent) ->
  channelRead(ctx, Object) with refcount release in finally.
  parseRequest signature now takes FullHttpRequest (HttpObjectAggregator
  emits FullHttpRequest); body bytes are copied out of the refcounted
  ByteBuf. writeResponse / serve404 / serve500 / serveStatic error fallback
  build DefaultFullHttpResponse so content can travel with the response;
  copyResponse keeps headers-only DefaultHttpResponse for the streaming
  paths (file / InputStream / ChunkedInput) and now flushes a trailing
  LastHttpContent.EMPTY_LAST_CONTENT to terminate the message.
  ctx.getChannel/getPipeline -> ctx.channel/pipeline; channel.write ->
  channel.writeAndFlush at terminal write sites; getStatus/getProtocolVersion/
  getMethod/getUri -> status/protocolVersion/method/uri.
  HttpHeaders.isKeepAlive -> HttpUtil.isKeepAlive.
  HttpHeaders.Names.* -> HttpHeaderNames.*; HttpHeaders.Values.WEBSOCKET ->
  HttpHeaderValues.WEBSOCKET. ChannelBuffers.copiedBuffer ->
  Unpooled.copiedBuffer; ChannelBuffer -> ByteBuf.
- LazyChunkedInput: implements ChunkedInput<ByteBuf> with the new
  readChunk(ByteBufAllocator) signature plus length()/progress(); legacy
  hasNextChunk()/nextChunk() retired.
- SslPlayHandler: channelConnected(ctx, ChannelStateEvent) -> channelActive(ctx).
  Stores the local socket address on a channel AttributeKey so SSLException
  redirects can build a useful Location URL. setEnableRenegotiation removed
  (renegotiation off by default in Netty 4). sslHandler.handshake() ->
  sslHandler.handshakeFuture(); SslListener now implements
  GenericFutureListener<Future<Channel>> to match handshakeFuture's type.
  exceptionCaught(ctx, ExceptionEvent) -> exceptionCaught(ctx, Throwable cause).
- FileService: ByteRangeInput implements ChunkedInput<ByteBuf>; nextChunk ->
  readChunk(ByteBufAllocator) returning a refcount-aware ByteBuf; trailing
  LastHttpContent.EMPTY_LAST_CONTENT sent after the chunked body.
  HttpHeaders.isKeepAlive -> HttpUtil.isKeepAlive; getStatus/getMethod/
  getProtocolVersion -> status/method/protocolVersion.
- FileChannelBuffer + StreamChunkAggregator: deleted. They were tightly
  coupled to Netty 3's ChannelBuffer + HttpChunk model; PF-32 will replace
  the disk-spooling logic against Netty 4's HttpContent/LastHttpContent
  message model.
- NettyPlayChannel: ctx.getChannel().setReadable(b) ->
  ctx.channel().config().setAutoRead(b).
- Http, F: org.jboss.netty.* -> io.netty.* import swaps (single line each).
- application-skel/conf/application.conf: documented default pipeline
  updated to the io.netty.* class names with HttpObjectAggregator.

Test:
- test-src/play/mvc/CookieDataCodecTest: org.jboss.netty.* -> io.netty.*
  for Cookie / ServerCookieDecoder.

Stage A intentionally caps aggregated request bodies at 1 MB and disables
WebSockets (501 stub). PF-32 restores large-body support; PF-33 restores
WebSockets and retires the deprecated Http.Inbound(ChannelHandlerContext)
ctor.

Verified with `ant clean unittest`: 295 tests pass, 0 failures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>