introduce standard admonitions on docs pages, with links to quickstart

[moxious]

The CSV plugin, while deprecated, is a big problem in our overall docs because it's got extreme Google SEO juice. Google "Grafana CSV" and you'll land here. In cloud data, we see a substantial number of people try & fail down this route. To that end, we wrote a simple blog post that tells people where to go the right way (use Infinity as we know).

In Grafana web data, we see CSV plugins docs still getting substantial traffic. This PR simply updates the admonition in the docs to point to a clean set of instructions/examples on "how to do CSV right", and then copies the admonition onto the docs pages. The goal is to gradually redirect users away from this approach over time, and towards the infinity approach.

[CLAassistant]

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[ivanahuckova]

@moxious thank you for contribution. I was not able to figure out failing CLA for Github Action here, so I recreated the PR #337. So closing this one in favour of #337.