Kube-prometheus: Ability to deploy blackbox_exporter as part of kube-prometheus

[RiRa12621]

What is missing?
A blackbox_exporter deployment
Why do we need it?
With the recent addition of synthetic probes, it is possible to easily create blackbox exporter probes, however this still requires a blackbox exporter deployment to exist on cluster in order to work.

Anything else we need to know?:
This is a follow up to https://github.com/prometheus-operator/prometheus-operator/issues/3514

[lilic]

cc @prometheus-operator/kube-prometheus-reviewers ^

[paulfantom]

SGTM to include this as a jsonnet patch. Similar to how we handle ksm-autoscaler: https://github.com/prometheus-operator/kube-prometheus/blob/master/jsonnet/kube-prometheus/ksm-autoscaler/ksm-autoscaler.libsonnet

[paulfantom]

@RiRa12621 if you want to pick this up, I uploaded a patch I was working on some time ago. It is available as a gist at https://gist.github.com/paulfantom/e27e79e294ca025748b05e5028b16346

[RiRa12621]

Thanks @paulfantom
I'll give it a shot next week

[tpalfalvi]

@RiRa12621 did you manage to make progress? If not, I have something that seems to work for me, I can try to make a PR from that.

[RiRa12621]

Was in COVID isolation apparently that didn't help getting things done.
Happy to see a PR from you, if you have it ready already @tpalfalvi