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/tlstool/tlstool_test.go

@@ -0,0 +1,92 @@
+package tlstool_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/tlstool"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/mockable"
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+)
+
+func TestMeasurerExperimentNameVersion(t *testing.T) {
+	measurer := tlstool.NewExperimentMeasurer(tlstool.Config{})
+	if measurer.ExperimentName() != "tlstool" {
+		t.Fatal("unexpected ExperimentName")
+	}
+	if measurer.ExperimentVersion() != "0.1.0" {
+		t.Fatal("unexpected ExperimentVersion")
+	}
+}
+
+func TestRunWithExplicitSNI(t *testing.T) {
+	ctx := context.Background()
+	measurer := tlstool.NewExperimentMeasurer(tlstool.Config{
+		SNI: "dns.google",
+	})
+	measurement := new(model.Measurement)
+	measurement.Input = "8.8.8.8:853"
+	err := measurer.Run(
+		ctx,
+		&mockable.Session{},
+		measurement,
+		model.NewPrinterCallbacks(log.Log),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRunWithImplicitSNI(t *testing.T) {
+	ctx := context.Background()
+	measurer := tlstool.NewExperimentMeasurer(tlstool.Config{})
+	measurement := new(model.Measurement)
+	measurement.Input = "dns.google:853"
+	err := measurer.Run(
+		ctx,
+		&mockable.Session{},
+		measurement,
+		model.NewPrinterCallbacks(log.Log),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestRunWithCancelledContext(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel() // cause failure
+	measurer := tlstool.NewExperimentMeasurer(tlstool.Config{})
+	measurement := new(model.Measurement)
+	measurement.Input = "dns.google:853"
+	err := measurer.Run(
+		ctx,
+		&mockable.Session{},
+		measurement,
+		model.NewPrinterCallbacks(log.Log),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sk, err := measurer.GetSummaryKeys(measurement)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := sk.(tlstool.SummaryKeys); !ok {
+		t.Fatal("invalid type for summary keys")
+	}
+}
+
+func TestSummaryKeysGeneric(t *testing.T) {
+	measurement := &model.Measurement{TestKeys: &tlstool.TestKeys{}}
+	m := &tlstool.Measurer{}
+	osk, err := m.GetSummaryKeys(measurement)
+	if err != nil {
+		t.Fatal(err)
+	}
+	sk := osk.(tlstool.SummaryKeys)
+	if sk.IsAnomaly {
+		t.Fatal("invalid isAnomaly")
+	}
+}