Allow passing a custom client-side dialer

[brandond]

Issue:

• Not able to connect to kubelet when using bind-address flag k3s-io/k3s#10444

Problem

Our remotedialer client needs to be able to provide a custom dialer for use when dialing connections on behalf of the server. Currently, the client dialer always uses an unconfigured net.Dialer{} struct, because there is no code path to call NewClientSessionWithDialer, meaning that s.dialer is always nil:

• remotedialer/session_serve.go

  Lines 45 to 56 in 40afe79

  	func (s *Session) clientConnect(ctx context.Context, message *message) error {
  	if s.auth == nil || !s.auth(message.proto, message.address) {
  	return errors.New("connect not allowed")
  	}
  	conn := newConnection(message.connID, s, message.proto, message.address)
  	s.addConnection(message.connID, conn)
  	go clientDial(ctx, s.dialer, conn, message)
  	return nil
  	}

• remotedialer/client_dialer.go

  Lines 20 to 25 in 40afe79

  	if dialer == nil {
  	d := net.Dialer{}
  	netConn, err = d.DialContext(ctx, message.proto, message.address)
  	} else {
  	netConn, err = dialer(ctx, message.proto, message.address)
  	}

Solution

Add ConnectToProxyWithDialer that calls NewClientSessionWithDialer so that callers can provide a custom local dialer function.

There is no change to the existing ConnectoToProxy function signature or behavior, as the current code path also just calls NewClientSessionWithDialer(auth, ws, nil)

CheckList

• Test