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/netx/resolver/saver_test.go

@@ -0,0 +1,211 @@
+package resolver_test
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"reflect"
+	"testing"
+	"time"
+
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/resolver"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
+)
+
+func TestSaverResolverFailure(t *testing.T) {
+	expected := errors.New("no such host")
+	saver := &trace.Saver{}
+	reso := resolver.SaverResolver{
+		Resolver: resolver.FakeResolver{
+			Err: expected,
+		},
+		Saver: saver,
+	}
+	addrs, err := reso.LookupHost(context.Background(), "www.google.com")
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+	if addrs != nil {
+		t.Fatal("expected nil address here")
+	}
+	ev := saver.Read()
+	if len(ev) != 2 {
+		t.Fatal("expected number of events")
+	}
+	if ev[0].Hostname != "www.google.com" {
+		t.Fatal("unexpected Hostname")
+	}
+	if ev[0].Name != "resolve_start" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[0].Time.Before(time.Now()) {
+		t.Fatal("the saved time is wrong")
+	}
+	if ev[1].Addresses != nil {
+		t.Fatal("unexpected Addresses")
+	}
+	if ev[1].Duration <= 0 {
+		t.Fatal("unexpected Duration")
+	}
+	if !errors.Is(ev[1].Err, expected) {
+		t.Fatal("unexpected Err")
+	}
+	if ev[1].Hostname != "www.google.com" {
+		t.Fatal("unexpected Hostname")
+	}
+	if ev[1].Name != "resolve_done" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[1].Time.After(ev[0].Time) {
+		t.Fatal("the saved time is wrong")
+	}
+}
+
+func TestSaverResolverSuccess(t *testing.T) {
+	expected := []string{"8.8.8.8", "8.8.4.4"}
+	saver := &trace.Saver{}
+	reso := resolver.SaverResolver{
+		Resolver: resolver.FakeResolver{
+			Result: expected,
+		},
+		Saver: saver,
+	}
+	addrs, err := reso.LookupHost(context.Background(), "www.google.com")
+	if err != nil {
+		t.Fatal("expected nil error here")
+	}
+	if !reflect.DeepEqual(addrs, expected) {
+		t.Fatal("not the result we expected")
+	}
+	ev := saver.Read()
+	if len(ev) != 2 {
+		t.Fatal("expected number of events")
+	}
+	if ev[0].Hostname != "www.google.com" {
+		t.Fatal("unexpected Hostname")
+	}
+	if ev[0].Name != "resolve_start" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[0].Time.Before(time.Now()) {
+		t.Fatal("the saved time is wrong")
+	}
+	if !reflect.DeepEqual(ev[1].Addresses, expected) {
+		t.Fatal("unexpected Addresses")
+	}
+	if ev[1].Duration <= 0 {
+		t.Fatal("unexpected Duration")
+	}
+	if ev[1].Err != nil {
+		t.Fatal("unexpected Err")
+	}
+	if ev[1].Hostname != "www.google.com" {
+		t.Fatal("unexpected Hostname")
+	}
+	if ev[1].Name != "resolve_done" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[1].Time.After(ev[0].Time) {
+		t.Fatal("the saved time is wrong")
+	}
+}
+
+func TestSaverDNSTransportFailure(t *testing.T) {
+	expected := errors.New("no such host")
+	saver := &trace.Saver{}
+	txp := resolver.SaverDNSTransport{
+		RoundTripper: resolver.FakeTransport{
+			Err: expected,
+		},
+		Saver: saver,
+	}
+	query := []byte("abc")
+	reply, err := txp.RoundTrip(context.Background(), query)
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+	if reply != nil {
+		t.Fatal("expected nil reply here")
+	}
+	ev := saver.Read()
+	if len(ev) != 2 {
+		t.Fatal("expected number of events")
+	}
+	if !bytes.Equal(ev[0].DNSQuery, query) {
+		t.Fatal("unexpected DNSQuery")
+	}
+	if ev[0].Name != "dns_round_trip_start" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[0].Time.Before(time.Now()) {
+		t.Fatal("the saved time is wrong")
+	}
+	if !bytes.Equal(ev[1].DNSQuery, query) {
+		t.Fatal("unexpected DNSQuery")
+	}
+	if ev[1].DNSReply != nil {
+		t.Fatal("unexpected DNSReply")
+	}
+	if ev[1].Duration <= 0 {
+		t.Fatal("unexpected Duration")
+	}
+	if !errors.Is(ev[1].Err, expected) {
+		t.Fatal("unexpected Err")
+	}
+	if ev[1].Name != "dns_round_trip_done" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[1].Time.After(ev[0].Time) {
+		t.Fatal("the saved time is wrong")
+	}
+}
+
+func TestSaverDNSTransportSuccess(t *testing.T) {
+	expected := []byte("def")
+	saver := &trace.Saver{}
+	txp := resolver.SaverDNSTransport{
+		RoundTripper: resolver.FakeTransport{
+			Data: expected,
+		},
+		Saver: saver,
+	}
+	query := []byte("abc")
+	reply, err := txp.RoundTrip(context.Background(), query)
+	if err != nil {
+		t.Fatal("we expected nil error here")
+	}
+	if !bytes.Equal(reply, expected) {
+		t.Fatal("expected another reply here")
+	}
+	ev := saver.Read()
+	if len(ev) != 2 {
+		t.Fatal("expected number of events")
+	}
+	if !bytes.Equal(ev[0].DNSQuery, query) {
+		t.Fatal("unexpected DNSQuery")
+	}
+	if ev[0].Name != "dns_round_trip_start" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[0].Time.Before(time.Now()) {
+		t.Fatal("the saved time is wrong")
+	}
+	if !bytes.Equal(ev[1].DNSQuery, query) {
+		t.Fatal("unexpected DNSQuery")
+	}
+	if !bytes.Equal(ev[1].DNSReply, expected) {
+		t.Fatal("unexpected DNSReply")
+	}
+	if ev[1].Duration <= 0 {
+		t.Fatal("unexpected Duration")
+	}
+	if ev[1].Err != nil {
+		t.Fatal("unexpected Err")
+	}
+	if ev[1].Name != "dns_round_trip_done" {
+		t.Fatal("unexpected name")
+	}
+	if !ev[1].Time.After(ev[0].Time) {
+		t.Fatal("the saved time is wrong")
+	}
+}