cleanup(netx): remove subpackages and unnecessary code (#788)

This pull request consists of several small and obvious cleanups in the netx directory.

See https://github.com/ooni/probe/issues/2121

internal/engine/netx/dialer_test.go

@@ -0,0 +1,48 @@
+package netx
+
+import (
+	"net/http"
+	"net/url"
+	"testing"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/bytecounter"
+	"github.com/ooni/probe-cli/v3/internal/netxlite"
+	"github.com/ooni/probe-cli/v3/internal/tracex"
+)
+
+func TestNewCreatesTheExpectedChain(t *testing.T) {
+	saver := &tracex.Saver{}
+	dlr := newDialer(&dialerConfig{
+		ContextByteCounting: true,
+		DialSaver:           saver,
+		Logger:              log.Log,
+		ProxyURL:            &url.URL{},
+		ReadWriteSaver:      saver,
+	}, netxlite.DefaultResolver)
+	bcd, ok := dlr.(*bytecounter.ContextAwareDialer)
+	if !ok {
+		t.Fatal("not a byteCounterDialer")
+	}
+	_, ok = bcd.Dialer.(*netxlite.MaybeProxyDialer)
+	if !ok {
+		t.Fatal("not a proxyDialer")
+	}
+	// We can safely stop here: the rest is tested by
+	// the internal/netxlite package
+}
+
+func TestDialerNewSuccess(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
+	log.SetLevel(log.DebugLevel)
+	d := newDialer(&dialerConfig{Logger: log.Log}, netxlite.DefaultResolver)
+	txp := &http.Transport{DialContext: d.DialContext}
+	client := &http.Client{Transport: txp}
+	resp, err := client.Get("http://www.google.com")
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+}