fix(dashboards): use new grafonnet for apiserver dashboard

[Duologic]

ref: #888

This updates the apiserver dashboard to use the new Grafonnet.

This will cause some changes but should result in the same dashboard.

A few noteable changes:

• Less 'defaults' are set, grafonnet-lib was quite verbose, the new grafonnet only adds the necessary.
• deprecated graph panel is replaced by timeSeries panel
• deprecated singlestat panel is replaced by the stat panel
• the 'row' structure is now calculated on the grid based on the width of the panels, it should match the original layout

The code abstracts a few of these panels into separate functions to avoid duplication a bit.

Also see inline comments about a few changes outside the dashboard.

[Duologic]

Grafana layout engine doesn't operate on 'rows' anymore (is really old), it now uses a grid system. I've included the defaults that exist in this file directly on the dashboard, we can generalize as more dashboards get ported.

[Duologic]

The linter wants that the Panel has a datasource set that matches the template variable, this is debatable. Panels do not really deal with datasources, the value at the panel level is passed through by the UI to the query targets.

When you only use one data source, this doesn't matter that much but when combining queries from multiple data sources on the same panel, then you have to set it to -- Mixed -- on the Panel level.

This is the what the new Grafonnet does, from a jsonnet/code perspective you'll see that the data source is configured on the query rather than the panel.

[povilasv]

Thanks for this, rebase needed :)

[Duologic]

Rebased, dropped a few commits.

[povilasv]

Thanks for this