GSoC 2022: Observasibility and Metrics

Please read the [Observasibility](https://github.com/apache/dubbo-awesome/blob/master/proposals/D4-observability.md) here first to know about the ultimate goal behind this issue.

If you are interested in this project and the objective described in the proposal, please leave comments below so we can further exchange information on the tasks that need to be done.

Start by reading proposals/D4-observability.md, then review the issue comments for the tasks and information exchanged. The issue does not identify entry points, files, tests, or a concrete completion criterion; scope and a definition of done would need to be established before implementation.

Written by the indexing model from the issue text.