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/dns_test.go

@@ -0,0 +1,142 @@
+package quicdialer_test
+
+import (
+	"context"
+	"crypto/tls"
+	"errors"
+	"net"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/lucas-clemente/quic-go"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/quicdialer"
+)
+
+type MockableResolver struct {
+	Addresses []string
+	Err       error
+}
+
+func (r MockableResolver) LookupHost(ctx context.Context, host string) ([]string, error) {
+	return r.Addresses, r.Err
+}
+
+func TestDNSDialerSuccess(t *testing.T) {
+	tlsConf := &tls.Config{NextProtos: []string{"h3-29"}}
+	dialer := quicdialer.DNSDialer{
+		Resolver: new(net.Resolver), Dialer: quicdialer.SystemDialer{}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com:443",
+		tlsConf, &quic.Config{})
+	if err != nil {
+		t.Fatal("unexpected error", err)
+	}
+	if sess == nil {
+		t.Fatal("non nil sess expected")
+	}
+}
+
+func TestDNSDialerNoPort(t *testing.T) {
+	tlsConf := &tls.Config{NextProtos: []string{"h3-29"}}
+	dialer := quicdialer.DNSDialer{
+		Resolver: new(net.Resolver), Dialer: quicdialer.SystemDialer{}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com",
+		tlsConf, &quic.Config{})
+	if err == nil {
+		t.Fatal("expected an error here")
+	}
+	if sess != nil {
+		t.Fatal("expected a nil sess here")
+	}
+	if err.Error() != "address www.google.com: missing port in address" {
+		t.Fatal("not the error we expected")
+	}
+}
+
+func TestDNSDialerLookupHostAddress(t *testing.T) {
+	dialer := quicdialer.DNSDialer{Resolver: MockableResolver{
+		Err: errors.New("mocked error"),
+	}}
+	addrs, err := dialer.LookupHost(context.Background(), "1.1.1.1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(addrs) != 1 || addrs[0] != "1.1.1.1" {
+		t.Fatal("not the result we expected")
+	}
+}
+
+func TestDNSDialerLookupHostFailure(t *testing.T) {
+	tlsConf := &tls.Config{NextProtos: []string{"h3-29"}}
+	expected := errors.New("mocked error")
+	dialer := quicdialer.DNSDialer{Resolver: MockableResolver{
+		Err: expected,
+	}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "dns.google.com:853",
+		tlsConf, &quic.Config{})
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+	if sess != nil {
+		t.Fatal("expected nil sess")
+	}
+}
+
+func TestDNSDialerInvalidPort(t *testing.T) {
+	tlsConf := &tls.Config{NextProtos: []string{"h3-29"}}
+	dialer := quicdialer.DNSDialer{
+		Resolver: new(net.Resolver), Dialer: quicdialer.SystemDialer{}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com:0",
+		tlsConf, &quic.Config{})
+	if err == nil {
+		t.Fatal("expected an error here")
+	}
+	if sess != nil {
+		t.Fatal("expected nil sess")
+	}
+	if !strings.HasSuffix(err.Error(), "sendto: invalid argument") &&
+		!strings.HasSuffix(err.Error(), "sendto: can't assign requested address") {
+		t.Fatal("not the error we expected")
+	}
+}
+
+func TestDNSDialerInvalidPortSyntax(t *testing.T) {
+	tlsConf := &tls.Config{NextProtos: []string{"h3-29"}}
+	dialer := quicdialer.DNSDialer{
+		Resolver: new(net.Resolver), Dialer: quicdialer.SystemDialer{}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com:port",
+		tlsConf, &quic.Config{})
+	if err == nil {
+		t.Fatal("expected an error here")
+	}
+	if sess != nil {
+		t.Fatal("expected nil sess")
+	}
+	if !errors.Is(err, strconv.ErrSyntax) {
+		t.Fatal("not the error we expected")
+	}
+}
+
+func TestDNSDialerDialEarlyFails(t *testing.T) {
+	tlsConf := &tls.Config{NextProtos: []string{"h3-29"}}
+	expected := errors.New("mocked DialEarly error")
+	dialer := quicdialer.DNSDialer{
+		Resolver: new(net.Resolver), Dialer: MockDialer{Err: expected}}
+	sess, err := dialer.DialContext(
+		context.Background(), "udp", "www.google.com:443",
+		tlsConf, &quic.Config{})
+	if err == nil {
+		t.Fatal("expected an error here")
+	}
+	if sess != nil {
+		t.Fatal("expected nil sess")
+	}
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected")
+	}
+}