refactor: pass experiment arguments using a struct (#983)

Closes https://github.com/ooni/probe/issues/2358.

internal/tutorial/experiment/torsf/chapter04/main.go

@@ -28,7 +28,12 @@ func main() {
 		MockableLogger:  log.Log,
 		MockableTempDir: tempdir,
 	}
-	if err = m.Run(ctx, sess, measurement, callbacks); err != nil {
+	args := &model.ExperimentArgs{
+		Callbacks:   callbacks,
+		Measurement: measurement,
+		Session:     sess,
+	}
+	if err = m.Run(ctx, args); err != nil {
 		log.WithError(err).Fatal("torsf experiment failed")
 	}
 	data, err := json.Marshal(measurement)

internal/tutorial/experiment/torsf/chapter04/torsf.go

@@ -99,10 +99,10 @@ type TestKeys struct {
 }
 
 // Run implements ExperimentMeasurer.Run.
-func (m *Measurer) Run(
-	ctx context.Context, sess model.ExperimentSession,
-	measurement *model.Measurement, callbacks model.ExperimentCallbacks,
-) error {
+func (m *Measurer) Run(ctx context.Context, args *model.ExperimentArgs) error {
+	callbacks := args.Callbacks
+	measurement := args.Measurement
+	sess := args.Session
 	testkeys := &TestKeys{}
 	measurement.TestKeys = testkeys
 	start := time.Now()