Migrate to stdlib ECH support

cmd/sing-box/cmd_generate_ech.go

@@ -9,8 +9,6 @@ import (
 	"github.com/spf13/cobra"
 )
 
-var pqSignatureSchemesEnabled bool
-
 var commandGenerateECHKeyPair = &cobra.Command{
 	Use:   "ech-keypair <plain_server_name>",
 	Short: "Generate TLS ECH key pair",
@@ -24,12 +22,11 @@ var commandGenerateECHKeyPair = &cobra.Command{
 }
 
 func init() {
-	commandGenerateECHKeyPair.Flags().BoolVar(&pqSignatureSchemesEnabled, "pq-signature-schemes-enabled", false, "Enable PQ signature schemes")
 	commandGenerate.AddCommand(commandGenerateECHKeyPair)
 }
 
 func generateECHKeyPair(serverName string) error {
-	configPem, keyPem, err := tls.ECHKeygenDefault(serverName, pqSignatureSchemesEnabled)
+	configPem, keyPem, err := tls.ECHKeygenDefault(serverName)
 	if err != nil {
 		return err
 	}