private String getNextBackupFileName() {
        SimpleDateFormat format = new SimpleDateFormat("yyyyMMddHHmmss");
        String dateStr = format.format(new Date(System.currentTimeMillis()));
        return DEFAULT_CONFIG_FILE + "." + dateStr;
    }
singleton for agent configuration.

@return static instance of AgentConfiguration
inlong-agent/agent-common/src/main/java/org/apache/inlong/agent/conf/AgentConfiguration.java