Custom Metrics Export Standardization

[louyuting]

Issue Description

Type: feature request

Describe what feature you want

Currently, the metrics is record in monitor log file。 We might need to standardize the metric export. So we could export the metrics information to downstream monitor system. Such as prometheus。

We might need standardize the interface. The way to downstream could be log file、kafka and so on,

The use case: K8s HPA

Additional context

Add any other context or screenshots about the feature request here.

[sczyh30]

A basic metric exporter abstraction and Prometheus exporter adapter have been introduced in #382. Further discussions are welcomed!