cleanup: remove unnecessary legacy interfaces (#656)

This diff addresses another point of https://github.com/ooni/probe/issues/1956:

> - [ ] observe that we're still using a bunch of private interfaces for common interfaces such as the `Dialer`, so we can get rid of these private interfaces and always use the ones in `model`, which allows us to remove a bunch of legacy wrappers

Additional cleanups may still be possible. The more I cleanup, the more I see
there's extra legacy code we can dispose of (which seems good?).

internal/engine/experiment/websteps/dns.go

@@ -5,13 +5,14 @@ import (
 
 	"github.com/apex/log"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx"
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 	"github.com/ooni/probe-cli/v3/internal/runtimex"
 )
 
 type DNSConfig struct {
 	Domain   string
-	Resolver netxlite.ResolverLegacy
+	Resolver model.Resolver
 }
 
 // DNSDo performs the DNS check.
@@ -22,7 +23,7 @@ func DNSDo(ctx context.Context, config DNSConfig) ([]string, error) {
 		runtimex.PanicOnError(err, "NewDNSClient failed")
 		resolver = childResolver
 		resolver = &netxlite.ResolverIDNA{
-			Resolver: netxlite.NewResolverLegacyAdapter(resolver),
+			Resolver: resolver,
 		}
 	}
 	return resolver.LookupHost(ctx, config.Domain)

internal/engine/experiment/websteps/factory.go

@@ -32,11 +32,11 @@ func NewRequest(ctx context.Context, URL *url.URL, headers http.Header) *http.Re
 
 // NewDialerResolver contructs a new dialer for TCP connections,
 // with default, errorwrapping and resolve functionalities
-func NewDialerResolver(resolver netxlite.ResolverLegacy) model.Dialer {
+func NewDialerResolver(resolver model.Resolver) model.Dialer {
 	var d model.Dialer = netxlite.DefaultDialer
 	d = &netxlite.ErrorWrapperDialer{Dialer: d}
 	d = &netxlite.DialerResolver{
-		Resolver: netxlite.NewResolverLegacyAdapter(resolver),
+		Resolver: resolver,
 		Dialer:   d,
 	}
 	return d
@@ -44,7 +44,7 @@ func NewDialerResolver(resolver netxlite.ResolverLegacy) model.Dialer {
 
 // NewQUICDialerResolver creates a new QUICDialerResolver
 // with default, errorwrapping and resolve functionalities
-func NewQUICDialerResolver(resolver netxlite.ResolverLegacy) model.QUICDialer {
+func NewQUICDialerResolver(resolver model.Resolver) model.QUICDialer {
 	var ql model.QUICListener = &netxlite.QUICListenerStdlib{}
 	ql = &netxlite.ErrorWrapperQUICListener{QUICListener: ql}
 	var dialer model.QUICDialer = &netxlite.QUICDialerQUICGo{
@@ -52,7 +52,7 @@ func NewQUICDialerResolver(resolver netxlite.ResolverLegacy) model.QUICDialer {
 	}
 	dialer = &netxlite.ErrorWrapperQUICDialer{QUICDialer: dialer}
 	dialer = &netxlite.QUICDialerResolver{
-		Resolver: netxlite.NewResolverLegacyAdapter(resolver),
+		Resolver: resolver,
 		Dialer:   dialer,
 	}
 	return dialer
@@ -79,12 +79,12 @@ func NewSingleTransport(conn net.Conn) http.RoundTripper {
 }
 
 // NewSingleTransport creates a new HTTP transport with a custom dialer and handshaker.
-func NewTransportWithDialer(dialer netxlite.DialerLegacy, tlsConfig *tls.Config, handshaker model.TLSHandshaker) http.RoundTripper {
+func NewTransportWithDialer(dialer model.Dialer, tlsConfig *tls.Config, handshaker model.TLSHandshaker) http.RoundTripper {
 	transport := newBaseTransport()
 	transport.DialContext = dialer.DialContext
 	transport.DialTLSContext = (&netxlite.TLSDialerLegacy{
 		Config:        tlsConfig,
-		Dialer:        netxlite.NewDialerLegacyAdapter(dialer),
+		Dialer:        dialer,
 		TLSHandshaker: handshaker,
 	}).DialTLSContext
 	return transport

internal/engine/experiment/websteps/quic.go

@@ -5,13 +5,14 @@ import (
 	"crypto/tls"
 
 	"github.com/lucas-clemente/quic-go"
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 type QUICConfig struct {
 	Endpoint   string
-	QUICDialer netxlite.QUICContextDialer
-	Resolver   netxlite.ResolverLegacy
+	QUICDialer model.QUICDialer
+	Resolver   model.Resolver
 	TLSConf    *tls.Config
 }
 

internal/engine/experiment/websteps/tcp.go

@@ -4,13 +4,14 @@ import (
 	"context"
 	"net"
 
+	"github.com/ooni/probe-cli/v3/internal/model"
 	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 type TCPConfig struct {
-	Dialer   netxlite.DialerLegacy
+	Dialer   model.Dialer
 	Endpoint string
-	Resolver netxlite.ResolverLegacy
+	Resolver model.Resolver
 }
 
 // TCPDo performs the TCP check.