refactor: move httpx into the internal package (#646)

This concludes the TODO list at https://github.com/ooni/probe/issues/1951

internal/netxlite/filtering/dns_test.go

@@ -11,8 +11,8 @@ import (
 	"github.com/apex/log"
 	"github.com/miekg/dns"
 	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
 	"github.com/ooni/probe-cli/v3/internal/model/mocks"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 func TestDNSProxy(t *testing.T) {

internal/netxlite/filtering/tls_test.go

@@ -9,8 +9,8 @@ import (
 	"testing"
 
 	"github.com/apex/log"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
 	"github.com/ooni/probe-cli/v3/internal/model/mocks"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 func TestTLSProxy(t *testing.T) {

internal/netxlite/filtering/tproxy_test.go

@@ -14,8 +14,8 @@ import (
 
 	"github.com/apex/log"
 	"github.com/ooni/probe-cli/v3/internal/model"
-	"github.com/ooni/probe-cli/v3/internal/netxlite"
 	"github.com/ooni/probe-cli/v3/internal/model/mocks"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
 )
 
 // tProxyDialerAdapter adapts a netxlite.TProxyDialer to be a netxlite.Dialer.