Explained in the pull request description.  Previously we only kept options' names for duplication check, but that didn't work under container environment.  We cache all `ChannelOption` instances for reuse now.  This introduces another problem.  The pool that keeps all `ChannelOption`s belongs to netty-transport while `UdtChannelOption` belongs to netty-transport-udt.  When netty-transport-udt is reloaded, there's no way to unload the `UdtChannelOption` instances kept by the pool, leading to `ClassCastException`.