feat(oonirun): implement OONIRun v1 (#843)

This diff adds support for running OONIRun v1 links.

Run with `miniooni` using:

```
./miniooni -i LINK oonirun
```

Part of https://github.com/ooni/probe/issues/2184

internal/oonirun/v1_test.go

@@ -0,0 +1,36 @@
+package oonirun
+
+import (
+	"context"
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/kvstore"
+)
+
+// 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 TestOONIRunV1Link(t *testing.T) {
+	ctx := context.Background()
+	config := &LinkConfig{
+		AcceptChanges: false,
+		Annotations: map[string]string{
+			"platform": "linux",
+		},
+		KVStore:     &kvstore.Memory{},
+		MaxRuntime:  0,
+		NoCollector: true,
+		NoJSON:      true,
+		Random:      false,
+		ReportFile:  "",
+		Session:     newSession(ctx, t),
+	}
+	r := NewLinkRunner(config, "https://run.ooni.io/nettest?tn=example&mv=1.2.0")
+	if err := r.Run(ctx); err != nil {
+		t.Fatal(err)
+	}
+	r = NewLinkRunner(config, "ooni://nettest?tn=example&mv=1.2.0")
+	if err := r.Run(ctx); err != nil {
+		t.Fatal(err)
+	}
+}