chore: merge probe-engine into probe-cli (#201)

This is how I did it:

1. `git clone https://github.com/ooni/probe-engine internal/engine`

2. ```
(cd internal/engine && git describe --tags)
v0.23.0
```

3. `nvim go.mod` (merging `go.mod` with `internal/engine/go.mod`

4. `rm -rf internal/.git internal/engine/go.{mod,sum}`

5. `git add internal/engine`

6. `find . -type f -name \*.go -exec sed -i 's@/ooni/probe-engine@/ooni/probe-cli/v3/internal/engine@g' {} \;`

7. `go build ./...` (passes)

8. `go test -race ./...` (temporary failure on RiseupVPN)

9. `go mod tidy`

10. this commit message

Once this piece of work is done, we can build a new version of `ooniprobe` that
is using `internal/engine` directly. We need to do more work to ensure all the
other functionality in `probe-engine` (e.g. making mobile packages) are still WAI.

Part of https://github.com/ooni/probe/issues/1335

internal/engine/experiment/run/run_test.go

@@ -0,0 +1,107 @@
+package run_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/dnscheck"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/run"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/urlgetter"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/mockable"
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+)
+
+func TestExperimentNameAndVersion(t *testing.T) {
+	measurer := run.NewExperimentMeasurer(run.Config{})
+	if measurer.ExperimentName() != "run" {
+		t.Error("unexpected experiment name")
+	}
+	if measurer.ExperimentVersion() != "0.2.0" {
+		t.Error("unexpected experiment version")
+	}
+}
+
+func TestRunDNSCheckWithCancelledContext(t *testing.T) {
+	measurer := run.NewExperimentMeasurer(run.Config{})
+	input := `{"name": "dnscheck", "input": "https://dns.google/dns-query"}`
+	measurement := new(model.Measurement)
+	measurement.Input = model.MeasurementTarget(input)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // fail immediately
+	sess := &mockable.Session{MockableLogger: log.Log}
+	callbacks := model.NewPrinterCallbacks(log.Log)
+	err := measurer.Run(ctx, sess, measurement, callbacks)
+	// TODO(bassosimone): here we could improve the tests by checking
+	// whether the result makes sense for a cancelled context.
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := measurement.TestKeys.(*dnscheck.TestKeys); !ok {
+		t.Fatal("invalid type for test keys")
+	}
+	sk, err := measurer.GetSummaryKeys(measurement)
+	if err != nil {
+		t.Fatal(err)
+	}
+	rsk, ok := sk.(dnscheck.SummaryKeys)
+	if !ok {
+		t.Fatal("cannot convert summary keys to specific type")
+	}
+	if rsk.IsAnomaly != false {
+		t.Fatal("unexpected IsAnomaly value")
+	}
+}
+
+func TestRunURLGetterWithCancelledContext(t *testing.T) {
+	measurer := run.NewExperimentMeasurer(run.Config{})
+	input := `{"name": "urlgetter", "input": "https://google.com"}`
+	measurement := new(model.Measurement)
+	measurement.Input = model.MeasurementTarget(input)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // fail immediately
+	sess := &mockable.Session{MockableLogger: log.Log}
+	callbacks := model.NewPrinterCallbacks(log.Log)
+	err := measurer.Run(ctx, sess, measurement, callbacks)
+	if err == nil {
+		t.Fatal(err)
+	}
+	if len(measurement.Extensions) != 6 {
+		t.Fatal("not the expected number of extensions")
+	}
+	tk, ok := measurement.TestKeys.(*urlgetter.TestKeys)
+	if !ok {
+		t.Fatal("invalid type for test keys")
+	}
+	if len(tk.DNSCache) != 0 {
+		t.Fatal("not the DNSCache value we expected")
+	}
+}
+
+func TestRunWithInvalidJSON(t *testing.T) {
+	measurer := run.NewExperimentMeasurer(run.Config{})
+	input := `{"name": }`
+	measurement := new(model.Measurement)
+	measurement.Input = model.MeasurementTarget(input)
+	ctx := context.Background()
+	sess := &mockable.Session{MockableLogger: log.Log}
+	callbacks := model.NewPrinterCallbacks(log.Log)
+	err := measurer.Run(ctx, sess, measurement, callbacks)
+	if err == nil || err.Error() != "invalid character '}' looking for beginning of value" {
+		t.Fatalf("not the error we expected: %+v", err)
+	}
+}
+
+func TestRunWithUnknownExperiment(t *testing.T) {
+	measurer := run.NewExperimentMeasurer(run.Config{})
+	input := `{"name": "antani"}`
+	measurement := new(model.Measurement)
+	measurement.Input = model.MeasurementTarget(input)
+	ctx := context.Background()
+	sess := &mockable.Session{MockableLogger: log.Log}
+	callbacks := model.NewPrinterCallbacks(log.Log)
+	err := measurer.Run(ctx, sess, measurement, callbacks)
+	if err == nil || err.Error() != "no such experiment: antani" {
+		t.Fatalf("not the error we expected: %+v", err)
+	}
+}