cleanup: remove ConnID, DialID, TransactionID (#395)

We are not using them anymore. The only nettest still using the
legacy netx implementation is tor, for which setting these fields
is useless, because it performs each measurement into a separate
goroutine. Hence, let us start removing this part of the legacy
netx codebase, which is hampering progress in other areas.

Occurred to me while doing testing for the recent changes in
error mapping (https://github.com/ooni/probe/issues/1505).

internal/engine/netx/quicdialer/dns.go

@@ -6,7 +6,6 @@ import (
 	"net"
 
 	"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/dialer"
 )
 
@@ -30,7 +29,6 @@ func (d DNSDialer) DialContext(
 	if tlsCfg.ServerName == "" {
 		tlsCfg.ServerName = onlyhost
 	}
-	ctx = dialid.WithDialID(ctx)
 	var addrs []string
 	addrs, err = d.LookupHost(ctx, onlyhost)
 	if err != nil {

internal/engine/netx/quicdialer/errorwrapper.go

@@ -5,7 +5,6 @@ import (
 	"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"
 )
 
@@ -18,13 +17,9 @@ type ErrorWrapperDialer struct {
 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 succeeded.
 		Classifier: errorx.ClassifyQUICFailure,
-		DialID:     dialID,
 		Error:      err,
 		Operation:  errorx.QUICHandshakeOperation,
 	}.MaybeBuild()

internal/engine/netx/quicdialer/errorwrapper_test.go

@@ -8,13 +8,12 @@ import (
 	"testing"
 
 	"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"
 	"github.com/ooni/probe-cli/v3/internal/engine/netx/quicdialer"
 )
 
 func TestErrorWrapperFailure(t *testing.T) {
-	ctx := dialid.WithDialID(context.Background())
+	ctx := context.Background()
 	d := quicdialer.ErrorWrapperDialer{
 		Dialer: MockDialer{Sess: nil, Err: io.EOF}}
 	sess, err := d.DialContext(
@@ -33,9 +32,6 @@ func errorWrapperCheckErr(t *testing.T, err error, op string) {
 	if !errors.As(err, &errWrapper) {
 		t.Fatal("cannot cast to ErrWrapper")
 	}
-	if errWrapper.DialID == 0 {
-		t.Fatal("unexpected DialID")
-	}
 	if errWrapper.Operation != op {
 		t.Fatal("unexpected Operation")
 	}
@@ -68,7 +64,7 @@ func TestErrorWrapperInvalidCertificate(t *testing.T) {
 }
 
 func TestErrorWrapperSuccess(t *testing.T) {
-	ctx := dialid.WithDialID(context.Background())
+	ctx := context.Background()
 	tlsConf := &tls.Config{
 		NextProtos: []string{"h3"},
 		ServerName: "www.google.com",