refactor(netxlite): hide details without breaking the rest of the tree (#454)

## Description

This PR continues the refactoring of `netx` under the following principles:

1. do not break the rest of the tree and do not engage in extensive tree-wide refactoring yet
2. move under `netxlite` clearly related subpackages (e.g., `iox`, `netxmocks`)
3. move into `internal/netxlite/internal` stuff that is clearly private of `netxlite`
4. hide implementation details in `netxlite` pending new factories
5. refactor `tls` code in `netxlite` to clearly separate `crypto/tls` code from `utls` code

After each commit, I run `go test -short -race ./...` locally. Each individual commit explains what it does. I will squash, but this operation will preserve the original commit titles, so this will give further insight on each step.

## Commits

* refactor: rename netxmocks -> netxlite/mocks

Part of https://github.com/ooni/probe/issues/1591

* refactor: rename quicx -> netxlite/quicx

See https://github.com/ooni/probe/issues/1591

* refactor: rename iox -> netxlite/iox

Regenerate sources and make sure the tests pass.

See https://github.com/ooni/probe/issues/1591.

* refactor(iox): move MockableReader to netxlite/mocks

See https://github.com/ooni/probe/issues/1591

* refactor(netxlite): generator is an implementation detail

See https://github.com/ooni/probe/issues/1591

* refactor(netxlite): separate tls and utls code

See https://github.com/ooni/probe/issues/1591

* refactor(netxlite): hide most types but keep old names as legacy

With this change we avoid breaking the rest of the tree, but we start
hiding some implementation details a bit. Factories will follow.

See https://github.com/ooni/probe/issues/1591

internal/engine/netx/dialer/bytecounter_test.go

@@ -9,8 +9,8 @@ import (
 	"testing"
 
 	"github.com/ooni/probe-cli/v3/internal/bytecounter"
-	"github.com/ooni/probe-cli/v3/internal/iox"
-	"github.com/ooni/probe-cli/v3/internal/netxmocks"
+	"github.com/ooni/probe-cli/v3/internal/netxlite/iox"
+	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
 )
 
 func dorequest(ctx context.Context, url string) error {
@@ -76,7 +76,7 @@ func TestByteCounterNoHandlers(t *testing.T) {
 }
 
 func TestByteCounterConnectFailure(t *testing.T) {
-	dialer := &byteCounterDialer{Dialer: &netxmocks.Dialer{
+	dialer := &byteCounterDialer{Dialer: &mocks.Dialer{
 		MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
 			return nil, io.EOF
 		},

internal/engine/netx/dialer/proxy_test.go

@@ -8,13 +8,13 @@ import (
 	"net/url"
 	"testing"
 
-	"github.com/ooni/probe-cli/v3/internal/netxmocks"
+	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
 )
 
 func TestProxyDialerDialContextNoProxyURL(t *testing.T) {
 	expected := errors.New("mocked error")
 	d := &proxyDialer{
-		Dialer: &netxmocks.Dialer{
+		Dialer: &mocks.Dialer{
 			MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
 				return nil, expected
 			},
@@ -45,7 +45,7 @@ func TestProxyDialerDialContextInvalidScheme(t *testing.T) {
 func TestProxyDialerDialContextWithEOF(t *testing.T) {
 	const expect = "10.0.0.1:9050"
 	d := &proxyDialer{
-		Dialer: &netxmocks.Dialer{
+		Dialer: &mocks.Dialer{
 			MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
 				if address != expect {
 					return nil, errors.New("unexpected address")

internal/engine/netx/dialer/saver_test.go

@@ -10,14 +10,14 @@ import (
 
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
 	"github.com/ooni/probe-cli/v3/internal/errorsx"
-	"github.com/ooni/probe-cli/v3/internal/netxmocks"
+	"github.com/ooni/probe-cli/v3/internal/netxlite/mocks"
 )
 
 func TestSaverDialerFailure(t *testing.T) {
 	expected := errors.New("mocked error")
 	saver := &trace.Saver{}
 	dlr := &saverDialer{
-		Dialer: &netxmocks.Dialer{
+		Dialer: &mocks.Dialer{
 			MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
 				return nil, expected
 			},
@@ -59,7 +59,7 @@ func TestSaverConnDialerFailure(t *testing.T) {
 	expected := errors.New("mocked error")
 	saver := &trace.Saver{}
 	dlr := &saverConnDialer{
-		Dialer: &netxmocks.Dialer{
+		Dialer: &mocks.Dialer{
 			MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
 				return nil, expected
 			},
@@ -79,9 +79,9 @@ func TestSaverConnDialerSuccess(t *testing.T) {
 	saver := &trace.Saver{}
 	dlr := &saverConnDialer{
 		Dialer: &saverDialer{
-			Dialer: &netxmocks.Dialer{
+			Dialer: &mocks.Dialer{
 				MockDialContext: func(ctx context.Context, network string, address string) (net.Conn, error) {
-					return &netxmocks.Conn{
+					return &mocks.Conn{
 						MockRead: func(b []byte) (int, error) {
 							return 0, io.EOF
 						},

internal/engine/netx/dialer/shaping_disabled.go

@@ -1,3 +1,4 @@
+//go:build !shaping
 // +build !shaping
 
 package dialer

internal/engine/netx/dialer/shaping_enabled.go

@@ -1,3 +1,4 @@
+//go:build shaping
 // +build shaping
 
 package dialer