Add agent info http

[observeralone]

Background

In the process of using Agent, we often need to know the Agent information we are using. Just like in the process of using the linux system, we often need to obtain the currently used version information through certain commands. We may get this information for troubleshooting or for other purposes, such as: megaease/easemesh#142

Demand

Add an http interface, through which you can get the information of the currently running EaseAgent, including the type and version at the beginning, and add options later as needed

Design

GET http://ip:port/agent-info
Response Body:

{
    "type": "EaseAgent",
    "version": "v2.2.1"
}