pie labels and labeldistance parameters

Currently the labels parameter of pie is used both for annotating the pie wedges directly, and for automatic legend entries. For consistency with other plotting methods, in future labels will only be used for the legend.

The labeldistance parameter will therefore default to None from Matplotlib 3.14, when it will also be deprecated and then removed in Matplotlib 3.16. To preserve the existing behavior for now, set labeldistance=1.1. For the longer term, to place labels on the wedges use the new wedge_labels and wedge_label_distance parameters of pie or the pie_label method. Note that pie_label allows for more customization of the label positions via the rotate and alignment parameters as well as distance.