[Feature] Support adding additional attr[0-4] for service level metrics

[wu-sheng]

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Description

Add attr[0-4] to all service level metrics through OAL and MAL metrics, and support customers to set these attrs through OAL filter(code extension) or MAL SampleFamily processes. To keep the costs limited, this feature would be totally optional, and we will only wave layer as attr0 for the default implementations. FYI @Fine0830 We will need UI side enhancement to add a new kind of widget to query layer-based TopN on the root dashboard to get the service list. And those services could jump into the service dashboard like the service table widget.

Use case

Currently, all service topN needs to be globally query. But, within v9 and v10, we introduced the layer concept, and many more monitoring are added. Then, people are wondering, whether SkyWalking would provide group or layer-based topN query? Sadly, we can't as service metrics(all metrics actually) don't have extra extension fields.

So, with this extension and MQE extension, we could have new expression such as service_cpm{attr0="general"} to get a layer-based topN.

Related issues

No response

Are you willing to submit a pull request to implement this on your own?

• [ ] Yes I am willing to submit a pull request on my own!

Code of Conduct

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