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/internal/mockable/mockable.go

@@ -0,0 +1,191 @@
+// Package mockable contains mockable objects
+package mockable
+
+import (
+	"context"
+	"net/http"
+	"net/url"
+
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/kvstore"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/psiphonx"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/runtimex"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/torx"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/tunnel"
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+	"github.com/ooni/probe-cli/v3/internal/engine/probeservices"
+	"github.com/ooni/probe-cli/v3/internal/engine/probeservices/testorchestra"
+)
+
+// Session allows to mock sessions.
+type Session struct {
+	MockableASNDatabasePath      string
+	MockableTestHelpers          map[string][]model.Service
+	MockableHTTPClient           *http.Client
+	MockableLogger               model.Logger
+	MockableMaybeResolverIP      string
+	MockableOrchestraClient      model.ExperimentOrchestraClient
+	MockableOrchestraClientError error
+	MockableProbeASNString       string
+	MockableProbeCC              string
+	MockableProbeIP              string
+	MockableProbeNetworkName     string
+	MockableProxyURL             *url.URL
+	MockableResolverIP           string
+	MockableSoftwareName         string
+	MockableSoftwareVersion      string
+	MockableTempDir              string
+	MockableTorArgs              []string
+	MockableTorBinary            string
+	MockableUserAgent            string
+}
+
+// ASNDatabasePath implements ExperimentSession.ASNDatabasePath
+func (sess *Session) ASNDatabasePath() string {
+	return sess.MockableASNDatabasePath
+}
+
+// GetTestHelpersByName implements ExperimentSession.GetTestHelpersByName
+func (sess *Session) GetTestHelpersByName(name string) ([]model.Service, bool) {
+	services, okay := sess.MockableTestHelpers[name]
+	return services, okay
+}
+
+// DefaultHTTPClient implements ExperimentSession.DefaultHTTPClient
+func (sess *Session) DefaultHTTPClient() *http.Client {
+	return sess.MockableHTTPClient
+}
+
+// KeyValueStore returns the configured key-value store.
+func (sess *Session) KeyValueStore() model.KeyValueStore {
+	return kvstore.NewMemoryKeyValueStore()
+}
+
+// Logger implements ExperimentSession.Logger
+func (sess *Session) Logger() model.Logger {
+	return sess.MockableLogger
+}
+
+// MaybeResolverIP implements ExperimentSession.MaybeResolverIP.
+func (sess *Session) MaybeResolverIP() string {
+	return sess.MockableMaybeResolverIP
+}
+
+// NewOrchestraClient implements ExperimentSession.NewOrchestraClient
+func (sess *Session) NewOrchestraClient(ctx context.Context) (model.ExperimentOrchestraClient, error) {
+	if sess.MockableOrchestraClient != nil {
+		return sess.MockableOrchestraClient, nil
+	}
+	if sess.MockableOrchestraClientError != nil {
+		return nil, sess.MockableOrchestraClientError
+	}
+	clnt, err := probeservices.NewClient(sess, model.Service{
+		Address: "https://ams-pg-test.ooni.org/",
+		Type:    "https",
+	})
+	runtimex.PanicOnError(err, "orchestra.NewClient should not fail here")
+	meta := testorchestra.MetadataFixture()
+	if err := clnt.MaybeRegister(ctx, meta); err != nil {
+		return nil, err
+	}
+	if err := clnt.MaybeLogin(ctx); err != nil {
+		return nil, err
+	}
+	return clnt, nil
+}
+
+// ProbeASNString implements ExperimentSession.ProbeASNString
+func (sess *Session) ProbeASNString() string {
+	return sess.MockableProbeASNString
+}
+
+// ProbeCC implements ExperimentSession.ProbeCC
+func (sess *Session) ProbeCC() string {
+	return sess.MockableProbeCC
+}
+
+// ProbeIP implements ExperimentSession.ProbeIP
+func (sess *Session) ProbeIP() string {
+	return sess.MockableProbeIP
+}
+
+// ProbeNetworkName implements ExperimentSession.ProbeNetworkName
+func (sess *Session) ProbeNetworkName() string {
+	return sess.MockableProbeNetworkName
+}
+
+// ProxyURL implements ExperimentSession.ProxyURL
+func (sess *Session) ProxyURL() *url.URL {
+	return sess.MockableProxyURL
+}
+
+// ResolverIP implements ExperimentSession.ResolverIP
+func (sess *Session) ResolverIP() string {
+	return sess.MockableResolverIP
+}
+
+// SoftwareName implements ExperimentSession.SoftwareName
+func (sess *Session) SoftwareName() string {
+	return sess.MockableSoftwareName
+}
+
+// SoftwareVersion implements ExperimentSession.SoftwareVersion
+func (sess *Session) SoftwareVersion() string {
+	return sess.MockableSoftwareVersion
+}
+
+// TempDir implements ExperimentSession.TempDir
+func (sess *Session) TempDir() string {
+	return sess.MockableTempDir
+}
+
+// TorArgs implements ExperimentSession.TorArgs.
+func (sess *Session) TorArgs() []string {
+	return sess.MockableTorArgs
+}
+
+// TorBinary implements ExperimentSession.TorBinary.
+func (sess *Session) TorBinary() string {
+	return sess.MockableTorBinary
+}
+
+// UserAgent implements ExperimentSession.UserAgent
+func (sess *Session) UserAgent() string {
+	return sess.MockableUserAgent
+}
+
+var _ model.ExperimentSession = &Session{}
+var _ probeservices.Session = &Session{}
+var _ psiphonx.Session = &Session{}
+var _ tunnel.Session = &Session{}
+var _ torx.Session = &Session{}
+
+// ExperimentOrchestraClient is the experiment's view of
+// a client for querying the OONI orchestra.
+type ExperimentOrchestraClient struct {
+	MockableFetchPsiphonConfigResult []byte
+	MockableFetchPsiphonConfigErr    error
+	MockableFetchTorTargetsResult    map[string]model.TorTarget
+	MockableFetchTorTargetsErr       error
+	MockableFetchURLListResult       []model.URLInfo
+	MockableFetchURLListErr          error
+}
+
+// FetchPsiphonConfig implements ExperimentOrchestraClient.FetchPsiphonConfig
+func (c ExperimentOrchestraClient) FetchPsiphonConfig(
+	ctx context.Context) ([]byte, error) {
+	return c.MockableFetchPsiphonConfigResult, c.MockableFetchPsiphonConfigErr
+}
+
+// FetchTorTargets implements ExperimentOrchestraClient.TorTargets
+func (c ExperimentOrchestraClient) FetchTorTargets(
+	ctx context.Context, cc string) (map[string]model.TorTarget, error) {
+	return c.MockableFetchTorTargetsResult, c.MockableFetchTorTargetsErr
+}
+
+// FetchURLList implements ExperimentOrchestraClient.FetchURLList.
+func (c ExperimentOrchestraClient) FetchURLList(
+	ctx context.Context, config model.URLListConfig) ([]model.URLInfo, error) {
+	return c.MockableFetchURLListResult, c.MockableFetchURLListErr
+}
+
+var _ model.ExperimentOrchestraClient = ExperimentOrchestraClient{}