Provide access to individual workflow runs

[lukas-mertens]

I had a look at https://github.com/grafana/github-datasource/pull/240/files and read over the source code. It seems like here:

you are only adding a aggregated version of the runs:

It is cool that you are already doing some calculations, but access to the raw workflow runs would be really important and useful. Here are a few usecases:

• Plot total pipeline time over time to monitor how it is developing
• Plot a state timeline of the pipeline status to get a time history of "is main green?"
• Plot a heatmap to see which jobs are failing often to find flaky jobs
• ...

So so many options. The github data source is such a cool thing, but I feel like the best actual value: Individual pipeline runs, best case broken down to the individual jobs, would be amazing and would enhance devops a lot!

As you already have a function in my linked pull request to gather such a list, you probably only have to call this method.