[bugfix] Release Netty buffers

[kciesielski]

During performance tests of Netty servers (#3434) I noticed log entries like:

[info] 2024-01-22 11:04:21,657 [epollEventLoopGroup-2-4] ERROR io.netty.util.ResourceLeakDetector - LEAK: ByteBuf.release() was not called before it's garbage-collected. See https://netty.io/wiki/reference-counted-objects.html for more information.
[info] Recent access records:
[info] Created at:
[info]  io.netty.buffer.SimpleLeakAwareByteBuf.unwrappedDerived(SimpleLeakAwareByteBuf.java:144)

This fix adds explicit release of resources, which makes the problematic logs go away. We'll look deeper into memory consumption with a profiler using performance tests.