Multi-series scalar pie charts

I have two questions which return single numbers that I've combined into a multi-series card, but it seems my only graphing options are a bar chart or funnel. Any reason pie charts aren't an option here? Row charts should probably be an option, too.

:arrow_down: Please click the :+1: reaction instead of leaving a `+1` or `update?` comment

No file or test is named. Start by locating the multi-series card chart-option handling and how existing bar and funnel choices are registered. Done means determining whether pie and row charts can be offered for multi-series scalar results and adding coverage for the supported options.

Written by the indexing model from the issue text.