Push of additionalScrapeConfigs to PrometheusAgent

[stijzermans]

Implement #2311, so both Prometheuses and PrometheusAgents can be updated with additionalScrapeConfigs.

How to test:

• Make sure prometheus-operator is installed and watching a namespace.
• Deploy PrometheusAgent in that watched namespace, through applying a manifest like:

apiVersion: monitoring.coreos.com/v1alpha1
kind: PrometheusAgent
metadata:
  name: prometheus-grafana-kube-pr-prometheus
spec:
  arbitraryFSAccessThroughSMs: {}
  externalUrl: http://prometheus-grafana-kube-pr-prometheus:9090
  hostNetwork: false
  image: quay.io/prometheus/prometheus:v2.54.1
  listenLocal: false
  logFormat: logfmt
  logLevel: info
  paused: false
  podMonitorNamespaceSelector: {}
  podMonitorSelector: {}
  portName: http-web
  probeNamespaceSelector: {}
  probeSelector: {}
  replicas: 1
  resources: {}
  routePrefix: /
  scrapeConfigNamespaceSelector: {}
  scrapeConfigSelector:
    matchLabels:
      release: prometheus-grafana
  scrapeInterval: 30s
  serviceAccountName: prometheus-grafana-kube-pr-prometheus
  serviceMonitorNamespaceSelector: {}
  serviceMonitorSelector: {}
  shards: 1
  version: v2.54.1
  walCompression: true

• Make sure at least PROMETHEUS_NAMESPACE is set in the minio-operator env to this watched namespace, minio-operator should then update the additionalScrapeConfigs attribute of the Prometheus agent when running.

[pjuarezd]

Looks good to me, is there any reason we are aware of to do not support PrometheusAgent @cesnietor?

[cesnietor]

LGTM we should support it. thanks for the PR.

[pjuarezd]

LGTM we should support it. thanks for the PR.

Thank you!, could you approve please? @cesnietor