refactor: move tlsdialer to netxlite (#404)

Part of https://github.com/ooni/probe/issues/1505

internal/engine/netx/tlsdialer/tls.go

@@ -66,41 +66,3 @@ func (h EmitterTLSHandshaker) Handshake(
 	})
 	return tlsconn, state, err
 }
-
-// TLSDialer is the TLS dialer
-type TLSDialer struct {
-	Config        *tls.Config
-	Dialer        UnderlyingDialer
-	TLSHandshaker TLSHandshaker
-}
-
-// DialTLSContext is like tls.DialTLS but with the signature of net.Dialer.DialContext
-func (d TLSDialer) DialTLSContext(ctx context.Context, network, address string) (net.Conn, error) {
-	// Implementation note: when DialTLS is not set, the code in
-	// net/http will perform the handshake. Otherwise, if DialTLS
-	// is set, we will end up here. This code is still used when
-	// performing non-HTTP TLS-enabled dial operations.
-	host, _, err := net.SplitHostPort(address)
-	if err != nil {
-		return nil, err
-	}
-	conn, err := d.Dialer.DialContext(ctx, network, address)
-	if err != nil {
-		return nil, err
-	}
-	config := d.Config
-	if config == nil {
-		config = new(tls.Config)
-	} else {
-		config = config.Clone()
-	}
-	if config.ServerName == "" {
-		config.ServerName = host
-	}
-	tlsconn, _, err := d.TLSHandshaker.Handshake(ctx, conn, config)
-	if err != nil {
-		conn.Close()
-		return nil, err
-	}
-	return tlsconn, nil
-}