Feat/Upgrade probe exporter with new blackbox_exporter image

[slopezz]

Related to https://github.com/3scale-ops/prometheus-exporter-operator/issues/40

• Upgrades blackbox_exporter image tag used in Probe PrometheusExporter to latest quay.io/prometheus/blackbox-exporter/v0.22.0
• Adds a new CR field called probeTargetLabel, used in grafana dashboard to distinguish among different targets
  • In the past, in order to monitor a target, it was used prometheus ServiceMonitor with a special relabeling config in order to have available target label

    relabelings:
    - sourceLabels: [__param_target]
    targetLabel: target

  • Now it can be used a newer and simpler prometheus Probe, which does not need any relabeling config, which already adds the monitored target with instance label
  • So, CR field probeTargetLabel permits to use any custom label to distinguish among targets
    • If you keep using a prometheus ServiceMonitor with a custom relabeling config, you can specify here which label are you using on the relabeling
    • If you use a simple prometheus Probe, you don't need to specify any value, because default value is already instance
  • In addition, until now with prometheus ServiceMonitor, the ServiceMonitor needed to live in the same namespace where Probe PrometheusExporter is deployed
  • Now with Probe it is not required, and so you can deploy the different Probes on different namespaces, so the namespace var used as a filter has been removed from the Grafana Dashboard
• Alpha release v0.5.1-alpha.4

/kind feature /priority important-soon /assign

[3scale-robot]

LGTM label has been added.

Git tree hash: bd0b0c883e8b9878ecde1554470fc5911d81d484

[slopezz]

/approve

[3scale-robot]

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