[Lens] Move "Tabular and single value" group to appear first in chart switcher

[MichaelMarcialis]

As a short term solution to address some concerns regarding the new Lens chart switcher design, let's move the "Tabular and single value" grouping of charts to appear first in the list for the chart switcher interface. The intent for doing so is to present more chart diversity immediately when opening the chart switcher, rather than having it be discovered via scrolling.

In the future, the intent will be to follow up with a more long-term solution that achieves the same display of diversity in a more visually impactful way. More on that to come later.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[wylieconlon]

This looks like a relatively simple change. We currently order the groups by their labels, but we can introduce a new property so that they can have a priority. So something like [{ groupLabel: "Tabular and single value", sortOrder: 1 }, { groupLabel: "Line and area" }]