feat: start sketching out the oonirun package (#842)

This diff refactors the ./internal/cmd/miniooni pkg and moves the code
for running experiments inside of the ./internal/oonirun pkg.

It's the first concrete step towards https://github.com/ooni/probe/issues/2184.

internal/oonirun/experiment_test.go

@@ -0,0 +1,60 @@
+package oonirun
+
+import (
+	"context"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/ooni/probe-cli/v3/internal/engine"
+	"github.com/ooni/probe-cli/v3/internal/kvstore"
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/version"
+)
+
+// TODO(bassosimone): it would be cool to write unit tests. However, to do that
+// we need to ~redesign the engine package for unit-testability.
+
+func newSession(ctx context.Context, t *testing.T) *engine.Session {
+	config := engine.SessionConfig{
+		AvailableProbeServices: []model.OOAPIService{},
+		KVStore:                &kvstore.Memory{},
+		Logger:                 model.DiscardLogger,
+		ProxyURL:               nil,
+		SoftwareName:           "miniooni",
+		SoftwareVersion:        version.Version,
+		TempDir:                os.TempDir(),
+		TorArgs:                []string{},
+		TorBinary:              "",
+		TunnelDir:              "",
+	}
+	sess, err := engine.NewSession(ctx, config)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return sess
+}
+
+func TestExperimentRunWithExample(t *testing.T) {
+	ctx := context.Background()
+	desc := &Experiment{
+		Annotations: map[string]string{
+			"platform": "linux",
+		},
+		ExtraOptions: map[string]any{
+			"SleepTime": int64(10 * time.Millisecond),
+		},
+		Inputs:         []string{},
+		InputFilePaths: []string{},
+		MaxRuntime:     0,
+		Name:           "example",
+		NoCollector:    true,
+		NoJSON:         true,
+		Random:         false,
+		ReportFile:     "",
+		Session:        newSession(ctx, t),
+	}
+	if err := desc.Run(ctx); err != nil {
+		t.Fatal(err)
+	}
+}