fix: add prometheus metric label "k8sgpt"

[JuHyung-Son]

Closes #363

📑 Description

add prometheus metric label to distinguish clusters.

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

i set label name as k8sgpt. and its value is k8sgpt.metadata.name. if there is more appropriate label name, please suggest.

example metric

# TYPE k8sgpt_reconcile_error_count counter
k8sgpt_reconcile_error_count{k8sgpt="gangnam1"} 13

[arbreezy]

I am wondering @JuHyung-Son if we have to update also chart's dashboard to include the filtering

[JuHyung-Son]

oh yes. it need to be updated.

[JuHyung-Son]

i added label on promql. but it needs to be tested.
since operator runs on local, not minikube, prometheus can not scrape new metrics.

[arbreezy]

It's a small change, it's fine I believe lets get it merged