Add io.netty.handler.codec.http2.Http2ConnectionHandler for runtime…

… GraalVM compilation (#9621)

Motivation:

Native image compilation is failing without extra flags:

```
Warning: Aborting stand-alone image build. No instances of io.netty.buffer.UnpooledHeapByteBuf are allowed in the image heap as this class should be initialized at image runtime. Object has been initialized by the io.netty.handler.codec.http2.Http2ConnectionHandler class initializer with a trace: 
 	at io.netty.buffer.Unpooled.wrappedBuffer(Unpooled.java:157)
	at io.netty.handler.codec.http2.Http2ConnectionHandler.<clinit>(Http2ConnectionHandler.java:74)
.  To fix the issue mark io.netty.buffer.UnpooledHeapByteBuf for build-time initialization with --initialize-at-build-time=io.netty.buffer.UnpooledHeapByteBuf or use the the information from the trace to find the culprit and --initialize-at-run-time=<culprit> to prevent its instantiation.

Detailed message:
Trace: 	object io.netty.buffer.ReadOnlyByteBuf
	object io.netty.buffer.UnreleasableByteBuf
	method io.netty.handler.codec.http2.Http2ConnectionHandler.access$500()
Call path from entry point to io.netty.handler.codec.http2.Http2ConnectionHandler.access$500(): 
	at io.netty.handler.codec.http2.Http2ConnectionHandler.access$500(Http2ConnectionHandler.java:66)
	at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.readClientPrefaceString(Http2ConnectionHandler.java:299)
	at io.netty.handler.codec.http2.Http2ConnectionHandler$PrefaceDecoder.decode(Http2ConnectionHandler.java:239)
	at io.netty.handler.codec.http2.Http2ConnectionHandler.decode(Http2ConnectionHandler.java:438)
	at io.netty.handler.codec.ByteToMessageDecoder.decodeRemovalReentryProtection(ByteToMessageDecoder.java:505)
	at io.netty.handler.codec.ByteToMessageDecoder.callDecode(ByteToMessageDecoder.java:444)
	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:283)
	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:374)
	at io.netty.channel.AbstractChannelHandlerContext.access$600(AbstractChannelHandlerContext.java:56)
	at io.netty.channel.AbstractChannelHandlerContext$7.run(AbstractChannelHandlerContext.java:365)
	at com.oracle.svm.core.jdk.RuntimeSupport.executeHooks(RuntimeSupport.java:144)
	at com.oracle.svm.core.jdk.RuntimeSupport.executeStartupHooks(RuntimeSupport.java:89)
	at com.oracle.svm.core.JavaMainWrapper.runCore(JavaMainWrapper.java:143)
	at com.oracle.svm.core.JavaMainWrapper.run(JavaMainWrapper.java:186)
	at com.oracle.svm.core.code.IsolateEnterStub.JavaMainWrapper_run_5087f5482cc9a6abc971913ece43acb471d2631b(generated:0)
```

Modification:

Add `io.netty.handler.codec.http2.Http2ConnectionHandler` for runtime compilation, as the buffer library's `io.netty.buffer.UnpooledHeapByteBuf` is also marked for runtime.

Result:

Native image compilation works again.

codec-http2/src/main/resources/META-INF/native-image/io.netty/codec-http2/native-image.properties

@@ -13,4 +13,4 @@
 # under the License.
 
 Args = --initialize-at-build-time=io.netty \
-       --initialize-at-run-time=io.netty.handler.codec.http2.Http2CodecUtil,io.netty.handler.codec.http2.Http2ClientUpgradeCodec,io.netty.handler.codec.http2.DefaultHttp2FrameWriter
+       --initialize-at-run-time=io.netty.handler.codec.http2.Http2CodecUtil,io.netty.handler.codec.http2.Http2ClientUpgradeCodec,io.netty.handler.codec.http2.Http2ConnectionHandler,io.netty.handler.codec.http2.DefaultHttp2FrameWriter