[prometheus-crds]: Migrate CustomResourceDefinitions to v1

[databus23]

For the upcoming k8s upgrade to 1.22 we need to migrate CustromResourceDefinitions to v1.

For some more details please check the 1.22 Deprecation Guide

There was also a post in the kubernetes blog about upcoming changes in 1.22:

Migrate to use the CustomResourceDefinition apiextensions.k8s.io/v1 API, available since v1.16.
You can use the v1 API to retrieve or update existing objects, even if they were created using an older API version. If you defined any custom resources in your cluster, those are still served after you upgrade.
If you're using external CustomResourceDefinitions, you can use kubectl convert to translate existing manifests to use the newer API. Because there are some functional differences between beta and stable CustomResourceDefinitions, our advice is to test out each one to make sure it works how you expect after the upgrade.

Happy hacking!