Allow option to display absolute values for pie chart #19338

Problem

I would like to show a label displaying the absolute numbers used to create the pie chart. Currently, only percentage labels are supported via autopct. Hacky solutions like https://stackoverflow.com/a/48299798/3779655 or https://stackoverflow.com/a/41089685/3779655 exist to retrieve the absolute values based from the fractional ones. It would be better to support it out of the box.

Proposed Solution

Add option wedgelabels=None|'percent'|'absolute'|list of strings together with wedgelabelfmt replacing autopct.

For migration, initialize wedgelabelfmt=autopct for wedgelabels='percent' and overwrite if wedgelabelfmt is set.