Add startup environment variable

[im-jinxinwang]

nacos版本： 2.2.1
添加启动变量的原因：
此版本必须指定NACOS_AUTH_IDENTITY_KEY、NACOS_AUTH_IDENTITY_VALUE、NACOS_AUTH_TOKEN环境变量才能正常启动。
报错日志：

ERROR Error starting Tomcat context. Exception: org.springframework.beans.factory.UnsatisfiedDependencyException. Message: Error creating bean with name 'authFilterRegistration' defined in class path resource [com/alibaba/nacos/core/auth/AuthConfig.class]: Unsatisfied dependency expressed through method 'authFilterRegistration' parameter 0; nested exception is org.springframework.beans.factory.UnsatisfiedDependencyException: Error creating bean with name 'authFilter' defined in class path resource [com/alibaba/nacos/core/auth/AuthConfig.class]: Unsatisfied dependency expressed through method 'authFilter' parameter 0; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'authConfigs': Injection of autowired dependencies failed; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'NACOS_AUTH_IDENTITY_KEY' in value "${NACOS_AUTH_IDENTITY_KEY}"