Stacked Pie Chart

**Describe the solution you'd like**
I'd like to request for a feature chart type for the road map : Stacked Pie chart.

A stacked pie chart, like a stacked line graph is useful to show segments of data or the breakdown of data into seperate segment whilst still showing the total. You can also use it to show progress within the segment ie. The overall segment has overall budget, and the stacked segment shows the progress or the usage of the segment.

Add any other context or screenshots about the feature request here.

Possible example : https://images.app.goo.gl/uxoFu2Z2sNZwKxFv8

The issue names no files or tests; start by reviewing the existing pie-chart implementation and chart APIs in the Flutter package. Compare the requested stacked behavior with the linked example, then define how totals, segments, and progress should be represented before implementation; done should mean the new chart type is supported and verified consistently with existing chart types.

Written by the indexing model from the issue text.