feat: support user defined ChannelFactory and forseResolveDNS

[qgjyf2001]

We need to do like this while writing Android VPN Service to protect our socket connection:

val javaNioChannel = SelectorProvider.provider().openSocketChannel()
val res = protect(javaNioChannel.socket())

In addition, VPN services also proxy DNS requests, so we need to directly connect to the DNS server within the proxy server

val dnsResolverGroup = object : DnsAddressResolverGroup(
            DnsNameResolverBuilder()
                .apply {
                    nameServerProvider(
                        SingletonDnsServerAddressStreamProvider(
                            InetSocketAddress("114.114.114.114", 53)
                        )
                    )
                    channelType(NioDatagramChannel::class.java)
                    queryTimeoutMillis(5000)
                    maxQueriesPerResolve(3)
                }
        ) {}

[monkeyWie]

LGTM