fix(poly): rm `Multipoly`

[cyphersnake]

Motivation Close #159

Overview

• Clean-up the project from two legacy modules
• fix test data (please check correctness of this)

[cyphersnake]

Let’s wait for the benchmark comparison before this PR

That's a reason not to merge it, but not to review it! :sweat_smile:

[cyphersnake]

The new algorithm is 31% faster than the old one for the trivial case study I'll provide benchmark later (it's remaster of trivial-example)