Improve cortex-tool analyse to handle more panel types and queries

[ttk]

I found that cortex-tool was generating a lot of errors in when analyzing our grafana instance with 300+ dashboards, where 75% of the dashboards had some parse error. We are using Grafana v8.2.3.

This MR basically eliminated all the errors I encountered when trying to analyse our grafana instance. There's a bit of voodoo when doing the regex variable replacement, but through trial and error I found a few rules that allow the parser to succeed so that the metric names can be extracted.

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