plugins: Add opencost plugin

[yolossn]

How to install opencost in cluster

1. Install prometheus using helm

helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm install prom prometheus-community/kube-prometheus-stack

2. Create a values.yaml

opencost:
  prometheus:
    internal:
      enabled: true
      namespaceName: default
      port: 9090
      serviceName: prom-kube-prometheus-stack-prometheus

3. Install opencost

helm repo add opencost https://opencost.github.io/opencost-helm-chart
helm install -f values.yaml my-opencost opencost/opencost

Video.Project.2.mp4

[joaquimrocha]

Left a couple of comments. I also think it should be nice to link to the instructions of how to set up OpenCost.
This could be done in the settings view, and we should have some way to warn the user about the need to set up OpenCost. E.g. a link "Please set up" instead of the value or ..., but this link should only be visible on hover (I think the new table supports this more easily). When OpenCost is not available and it's not configured, I think we should have ! as the value. So users do not think the values are still loading.

[yolossn]

Adding few screenshots for reference.

[joaquimrocha]

Found that the main.js is checked in, when it should not.
Also please rebase since there are now fixes in main for CI issues.

[yolossn]