[backport] fix(registry): mark torsf as disabled by default

This diff backports #1359 to the release/3.19 branch.

There may be upcoming changes in torsf which may cause it to fail
consistently as it occurred during the 3.18 cycle.

Therefore, be defensive and make it disabled by default.

Part of ooni/probe#2553

While there, use slightly better naming for an echcheck function.

internal/experiment/echcheck/handshake.go

@@ -37,7 +37,7 @@ func handshakeWithEch(ctx context.Context, conn net.Conn, zeroTime time.Time,
 	return handshakeWithExtension(ctx, conn, zeroTime, address, sni, []utls.TLSExtension{&utlsEchExtension}, logger)
 }
 
-func handshakeMaybePrintECH(doprint bool) string {
+func handshakeMaybePrintWithECH(doprint bool) string {
 	if doprint {
 		return "WithECH"
 	}
@@ -51,7 +51,7 @@ func handshakeWithExtension(ctx context.Context, conn net.Conn, zeroTime time.Ti
 	handshakerConstructor := newHandshakerWithExtensions(extensions)
 	tracedHandshaker := handshakerConstructor(log.Log, &utls.HelloFirefox_Auto)
 
-	ol := logx.NewOperationLogger(logger, "echcheck: TLSHandshake%s", handshakeMaybePrintECH(len(extensions) > 0))
+	ol := logx.NewOperationLogger(logger, "echcheck: TLSHandshake%s", handshakeMaybePrintWithECH(len(extensions) > 0))
 	start := time.Now()
 	maybeTLSConn, err := tracedHandshaker.Handshake(ctx, conn, tlsConfig)
 	finish := time.Now()

internal/registry/factory_test.go

@@ -481,8 +481,11 @@ func TestNewFactory(t *testing.T) {
 			inputPolicy:      model.InputNone,
 		},
 		"torsf": {
-			enabledByDefault: true,
-			inputPolicy:      model.InputNone,
+			// We suspect there will be changes in torsf SNI soon. We are not prepared to
+			// serve these changes using the check-in API. Hence, disable torsf by default
+			// and require enabling it using the check-in API feature flags.
+			//enabledByDefault: false,
+			inputPolicy: model.InputNone,
 		},
 		"urlgetter": {
 			enabledByDefault: true,

internal/registry/torsf.go

@@ -17,7 +17,7 @@ func init() {
 			)
 		},
 		config:           &torsf.Config{},
-		enabledByDefault: true,
+		enabledByDefault: false,
 		inputPolicy:      model.InputNone,
 	}
 }