Allow custom `SocketOption`s to be set and get

[idelpivnitskiy]

We allow users to set SocketOptions on the client/server builder and to query SocketOptions on ConnectionContext API. Currently, these methods support only SocketOption constants from java.net.StandardSocketOptions and io.servicetalk.transport.api.ServiceTalkSocketOptions. However, the java.net.SocketOption API is generic and we should allow users to provide a custom implementation of this interface. We can match it with the ChannelOption that netty uses internally.