Auto detection and use of epoll for ELG

I know it's possible to pass in a custom ELG to the NettyServerBuilder, but it'd be great if by adding a dependency on the proper packages if the DefaultELGResource would just use reflection and use epoll instead. If I were to submit a PR, is this something that would be accepted?

Start with NettyServerBuilder and DefaultELGResource to understand how a custom event loop group is currently selected. Check the existing dependency and reflection boundaries around epoll, then determine the expected behavior when the proper packages are present. Done means the issue has an agreed implementation scope and verified automatic epoll selection without requiring a custom ELG.

索引モデルが issue の本文から書いたものです。