Add autoscaling prometheus

[vyzigold]

This pull request adds a new api. This api will be used for the planed autoscaling feature.

Part of this PR is:

• Possibility to automatically deploy prometheus with the help of the observability-operator (it's assumed, that the operator is already installed)
• The PR also allows to specify a user-deployed prometheus by specifying the host and port parameters.
• The whole autoscaling can be enabled and disabled by the autoscaling.enabled parameter. Right now I left it disabled by default. Because the autoscaling feature will need more PRs to start working.

In the upcoming PRs this api will by extended to also deploy aodh and a service / pod monitor to get the autoscaling data to the prometheus.

[openshift-ci]

Hi @vyzigold. Thanks for your PR.

I'm waiting for a openstack-k8s-operators member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[paramite]

Didn't test this yet, but seems legit.

[vyzigold]

I rebased on top of master.

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: paramite, vyzigold

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