PieChart doesn't show custom legend

[kajsa-work]

Describe the bug
Custom legend is not applied to PieChart.

To Reproduce

1. Create a custom legend using the guide: Custom legends.

2. Add the legend to a cartesian chart as well as a pie chart:

<lvc:CartesianChart Series="{Binding Series}">
  <lvc:CartesianChart.Legend>
    <local:Legend/>
  </lvc:CartesianChart.Legend>
</lvc:CartesianChart>

<lvc:PieChart Series="{Binding Series2}">
  <lvc:PieChart.Legend>
    <local:Legend/>
  </lvc:PieChart.Legend>
</lvc:PieChart>

3. The Cartesian chart will have the custom legend, but the Pie chart will have the default one.

Expected behavior
PieChart should have the same legend style as the cartesian chart

Screenshots

Desktop (please complete the following information):
WPF, version 2.0.0-rc2

[bsilvia]

This is related to #985 and was partially fixed with #859 for the CartesianChart control but not the PieChart or PolarChart controls.