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/quicdialer/errorwrapper.go

@@ -0,0 +1,34 @@
+package quicdialer
+
+import (
+	"context"
+	"crypto/tls"
+
+	"github.com/lucas-clemente/quic-go"
+	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/dialid"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/errorx"
+)
+
+// ErrorWrapperDialer is a dialer that performs quic err wrapping
+type ErrorWrapperDialer struct {
+	Dialer ContextDialer
+}
+
+// DialContext implements ContextDialer.DialContext
+func (d ErrorWrapperDialer) DialContext(
+	ctx context.Context, network string, host string,
+	tlsCfg *tls.Config, cfg *quic.Config) (quic.EarlySession, error) {
+	dialID := dialid.ContextDialID(ctx)
+	sess, err := d.Dialer.DialContext(ctx, network, host, tlsCfg, cfg)
+	err = errorx.SafeErrWrapperBuilder{
+		// ConnID does not make any sense if we've failed and the error
+		// does not make any sense (and is nil) if we succeded.
+		DialID:    dialID,
+		Error:     err,
+		Operation: errorx.QUICHandshakeOperation,
+	}.MaybeBuild()
+	if err != nil {
+		return nil, err
+	}
+	return sess, nil
+}