IGNITE-15162 Thin 3.0: Add buffer pooling (#252)

* Add server-side and client-side buffer pooling using Netty ByteBuf pooled allocator.
  * https://netty.io/wiki/using-as-a-generic-library.html
  * https://netty.io/wiki/reference-counted-objects.html
* Prepend message length in `ClientMessagePacker` to avoid extra buffer allocation and get rid of `ClientMessageEncoder`.
* Move request handling to separate classes (one class per message type).
* Stop `ConfigurationRegistry` after tests.
29 files changed