Support proxy and onion

[eval-exec]

This PR introduces and supports Onion3 multiaddr for tentacle-multiaddr and adds socks5 proxy support for tentacle dialing. It also allows tentacle to connect to a Tor server to reach an onion address.

A breaking change introduced is:

1. Changing

   pub(crate) type TcpSocketConfig =
       Arc<dyn Fn(TcpSocket) -> Result<TcpSocket, std::io::Error> + Send + Sync + 'static>;

   to:

   pub(crate) type TcpSocketTransformer =
       Arc<dyn Fn(TcpSocket) -> Result<TcpSocket, std::io::Error> + Send + Sync + 'static>;
   
   pub(crate) struct TcpSocketConfig {
       pub(crate) socket_transformer: TcpSocketTransformer,
       pub(crate) proxy_config: Option<ProxyConfig>,
   }

2. Adding an Onion variant to the TransportType enum and implementing OnionTransport.

3. Allow runtime::connect to use a socks5 proxy for connecting to the target address.

4. Add runtime::connect_onion to connect to a target address of the Multiaddr type, rather than just a SocketAddr, since tentacle cannot convert an onion address into a SocketAddr.