Consider implementing `client.Dialer()`

It would be pretty neat to have all protocols have a way to return a `net.Dialer` for forwarding traffic.

On SSH it comes pretty much out-of-the-box, on localhost it can just return it from stdlib `net`. On `openssh` it's probably easy-ish, but on WinRM it needs some kind of powershell scriptlet that opens a `System.Net.Sockets.TcpClient` and streams stdin/stdout.

This could be used for bastion and for communicating to APIs.

Start by reading the existing client and protocol interfaces, then compare the SSH, localhost, openssh, and WinRM implementations. Clarify how each should provide a net.Dialer, including the WinRM PowerShell TcpClient approach. Done means the supported protocols can return dialers for bastion and API traffic.

Written by the indexing model from the issue text.