[Feature] [Status API] add alarm runtime status API to increase in-memory data visibility

[wu-sheng]

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• I had searched in the issues and found no similar feature requirement.

Description

We are running alarm in memory, so, it is hard to review its runtime status, such as whether rules affected, which data is in memory windows.
I plan to add these APIs to help this

1. /status/alarm/rules, list all available rules.
2. /status/alarm/{rule-id}, outputs rules, and affected entities in memory
3. /status/alarm/{rule-id}/{entity-name}, output rules with running context.

Use case

With the combination of 3 these APIs, we could debug alarm running context per oap node manually

Related issues

With this information, we could tell whether cluster coordinator runs as expected by manual check.

We could add an extra segment of cluster management called check cluster scale to use this API to check that.

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

• I agree to follow this project's Code of Conduct