Provide connect function which exposes new mux interface

The current [connectTo](https://github.com/input-output-hk/ouroboros-network/blob/master/ouroboros-network/src/Ouroboros/Network/NodeToClient.hs#L227) is using the compatibility mode of the multiplexer, which forces the caller to run all mini-protocols, and requires to synchronize their termination (if one terminates then all other multiplexed mini-protocols shut down), which is not convenient for local clients.