refactor: move tunnel pkg down one level (#358)

* refactor: move tunnel pkg down one level

While there, reduce unnecessary dependency on external packages.

* file I forgot to commit

internal/tunnel/tor_integration_test.go

@@ -0,0 +1,52 @@
+package tunnel_test
+
+import (
+	"context"
+	"io/ioutil"
+	"testing"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/engine"
+	"github.com/ooni/probe-cli/v3/internal/tunnel"
+	"golang.org/x/sys/execabs"
+)
+
+func TestTorStartStop(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skip test in short mode")
+	}
+	torBinaryPath, err := execabs.LookPath("tor")
+	if err != nil {
+		t.Skip("missing precondition for the test: tor not in PATH")
+	}
+	tunnelDir, err := ioutil.TempDir("testdata", "tor")
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx := context.Background()
+	sess, err := engine.NewSession(ctx, engine.SessionConfig{
+		Logger:          log.Log,
+		SoftwareName:    "miniooni",
+		SoftwareVersion: "0.1.0-dev",
+		TunnelDir:       tunnelDir,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	tunnel, err := tunnel.Start(context.Background(), &tunnel.Config{
+		Name:      "tor",
+		Session:   sess,
+		TorBinary: torBinaryPath,
+		TunnelDir: tunnelDir,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if tunnel.SOCKS5ProxyURL() == nil {
+		t.Fatal("expected non nil URL here")
+	}
+	if tunnel.BootstrapTime() <= 0 {
+		t.Fatal("expected positive bootstrap time here")
+	}
+	tunnel.Stop()
+}