Remove pingcap/errors dependency in favor of stdlib (#6)

Author: kyleconroy

ast/annotate.go

@@ -0,0 +1,30 @@
+// Copyright 2025 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ast
+
+import "fmt"
+
+func annotate(err error, msg string) error {
+	if err == nil {
+		return nil
+	}
+	return fmt.Errorf("%s: %w", msg, err)
+}
+
+func annotatef(err error, format string, args ...any) error {
+	if err == nil {
+		return nil
+	}
+	return fmt.Errorf("%s: %w", fmt.Sprintf(format, args...), err)
+}