[tracking] Admin Interface

[ihciah]

Like envoy, we can expose admin interface to make it able to push new configuration, observe internal state or control log level, etc.

1. It is a independent module which can be used by users freely.
2. Users can register handler to it.
3. It can bind to uds or tcp.
4. It can interactive with general metric module [tracking] General Metric Module #87 .

[goldenrye]

what's the status of this feature? can we move to the next release?