[#394] Eliminate QuickCheck dependency

Description

This MR removes a lot of deprecated (explicitly or implicitly) QuickCheck-related stuff. Functions were explicitly deprecated long ago. Instances were implicitly deprecated, we decided to remove them at some point long ago.

Bonus: also removed Lorentz.TestScenario because it's an old thing that is useless nowadays.

Related issue(s)

Resolves #394 (closed)

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