Change automatic color generation for Voronoiplot

[DanielVandH]

Description

Fixes https://github.com/MakieOrg/Makie.jl/issues/4344 by using a consistent method for generating colors. Using this approach the colors will be consistent between plots even if generators were removed or added. The old approach wasn't optimal since the Set defining each_generator(vorn) isn't ordered consistently across tessellations if the generator set changed.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

Checklist

• [x] Added an entry in CHANGELOG.md (for new features and breaking changes)
• [x] Added or changed relevant sections in the documentation
• [x] Added unit tests for new algorithms, conversion methods, etc.
• [ ] Added reference image tests for new plotting functions, recipes, visual options, etc.