Create basic Grafana dashboard with all available metrics

[Nutomic]

Summary of changes

• Add basic Grafana dashboard which shows all available metrics (except resource_metric_map #387)

I tried to get some actual stats by running tests, but still everything shows zero. I guess that it will work better by connecting to a live relayer. The specific way things are visualized can also be improved in the future.

Reference issue to close (if applicable)

• Closes https://github.com/webb-tools/relayer/issues/388

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Code Checklist

• [ ] Tested
• [ ] Documented