Add runtime benchmark historical chart to the dashboard

[Kobzol]

The dashboard currently contains data for check/debug/opt/doc builds. It would be nice to also add a historical chart for our runtime benchmarks to it (probably with the wall-time metric, same as for the compile benchmarks).

[s7tya]

As mentioned in #1901, the graph width is a bit large, and there would be many graphs if we add runtime ones. It might be a good idea to arrange the charts in two columns when adding runtime charts.

[Kobzol]

Could be, or we can add some mini-index, or make the individual charts collapsable. Whatever works :)