MonitorMetrics report by http

[zouyingjie]

Now the monitoring metrics of easegress can be reported through Kafka.

- kafka:
    brokers:
    - 172.10.1.111:9092
    - 172.10.1.112:9092
    - 172.10.1.113:9092
    topic: metrics-topic
  kind: EaseMonitorMetrics
  name: EaseMonitorMetrics-default

Easegress and Kafka may be in different network environments, so they may need to report indicators through the public network. However, exposing Kafka to the public network is not a good practice, so it needs to be forwarded through an external gateway.

Therefore, easegress needs to support reporting data via HTTP and configuring HTTP basic and mTLS.

[xxx7xxxx]

@zouyingjie Is the requirement still relevant?