CLOUD-845 Added a doc how to troubleshoot Operator installation

[nastena1606]

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[render]

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[fiowro]

The doc is good, but I think it needs a little bit different name. Here we are troubleshooting the Kubernetes cluster (or Kubernetes environment, you may say). The "installation" word is used in our TOC to point at the installation process, not the environment.

Also, putting this to the 1st place in the troubleshooting subsection in TOC is questionable. First we have this doc, and then we have initial troubleshooting. I'd recommend naming this as "Kubernetes troubleshooting" and putting it to the very end of the subsection. Reasons for such a placement: It's a supplementary doc, it is not about our Operator; also, env troubleshooting is a rare thing to do, compared with our other troubleshooting docs.