enable Netty leak detector extension

[sullis]

Proof of concept :)

OSS library: https://github.com/nettyplus/netty-leak-detector-junit-extension

[sullis]

I observed a failure in GitHub Actions

ubuntu-20.04

Http2Tests > testHttp2ForMemoryLeaks() FAILED
    java.lang.IllegalStateException: Netty leaks: after [testHttp2ForMemoryLeaks()] [ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf]
        at io.github.nettyplus.leakdetector.junit.NettyLeakListener.assertZeroLeaks(NettyLeakListener.java:31)

[sullis]

GitHub Actions CI:

Http2Tests > testHttp2ForMemoryLeaks() FAILED
    java.lang.IllegalStateException: Netty leaks: after [testHttp2ForMemoryLeaks()] [ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf, ByteBuf]
        at io.github.nettyplus.leakdetector.junit.NettyLeakListener.assertZeroLeaks(NettyLeakListener.java:31)