Partition nested legends are not depicted well when there are same values per metric

[stratoula]

Describe the bug
I have created a Lens pie chart with two layers. While the pie chart is rendered correctly I can see on the legend bar (with the nested switch on) that the nested legends are not displayed correctly. Some of the values are repeated with a color of a different series.

Here the problem is more obvious:

To Reproduce
Steps to reproduce the behavior:

1. Go to Kibana Lens
2. Select the kibana_sample_data_logs dataset
3. Drag and drop the machine.os.keyword and the memory fields
4. Switch on the nested legend from the top menu
5. Check that the legends are not displayed correctly

Expected behaviour
The nested legends should appear without duplicates from other series.

Additional context
I have also found out this problem on migrating the vislib pie chart to the es-charts one.

Kibana cross-issue
elastic/kibana#84307

[flash1293]

I can reproduce this outside of Lens as well: https://codesandbox.io/s/little-leaf-05w34?file=/src/App.tsx

[monfera]

Note to self, check the condition Marco references here: #939 (comment)

[monfera]

Fixed by #947